How do you measure a Class Triple-A player against a Low Class A player when judging who the better prospect is?

Do you look strictly at performance? Or purely potential? Or some amorphous combination of the two? The test I find myself applying when ranking Rangers' prospects is simple: Who would I least want to see in an Angels or A's uniform?

Now that my favorite Rangers pitching prospect in years, Derek Holland, has made it to Arlington, I've been thinking for a few weeks about who my new number one pitching prospect in the system is. For most, it's unquestionably Neftali Feliz, but for me it's not a necessarily easy decision.

If Toronto were to come to me and make Roy Halladay available, for instance, in a trade that had to include Feliz or Hickory left-hander Martin Perez -- my choice -- I'm really not sure which way I'd go. The way I judge prospects, I answer for myself the question of which player would give me a bigger stomach ache to lose to a division rival, and that's how I decide, unscientifically, how to slot these guys.

This week's Top 20 Rangers prospects:

1. JUSTIN SMOAK, 1B, Double-A Frisco (number 1 last week)

The arrival of Bakersfield slugger Mitch Moreland in Frisco on Tuesday wasn't accompanied by a Smoak promotion to AAA, and not solely because of Smoak's mild oblique strain (which has kept him off the field since Saturday). Moreland is expected to play mostly on an outfield corner while Smoak continues to man first base. The minor injury to the switch-hitting plate monster has his numbers frozen for the moment at .324/.443/.500.

2. MARTIN PEREZ, LHP, Low A Hickory (3)

I'm ready to call Perez the top pitching prospect in the system. No knock on Neftali Feliz, but Perez has been as dominant in Low Class A at age 18 as Feliz was at the same level last year at age 20. Perez fanned nine Hagerstown hitters in four scoreless innings for Hickory on Monday, giving him 50 strikeouts and 14 walks in 40.2 innings of work, almost identical to Feliz's Clinton rate in 2008 (106 strikeouts and 28 walks in 82 innings). Perez's .214 opponents' average, 1.83 G/F, and 2.43 ERA compare well with Feliz's .193/1.64/2.52 marks, and while Perez doesn't touch triple digits, he does complement mid-90s velocity with a better set of secondary offerings. If I had to trade one of them, the decision wouldn't be easy.

3. NEFTALI FELIZ, RHP, Triple-A Oklahoma City (2)

Two very good starts after Feliz's return from minor shoulder soreness (two runs on five hits and two walks in 11 innings, with 11 strikeouts) were followed by one that started well but broke down quickly. Feliz allowed two hits in a scoreless first inning on Tuesday, after which he set Reno down in order in the second and third, but in the fourth, he lost his command, giving up a one-out single before issuing three walks in the space of four hitters, ending his night. Overcoming the first command issues of his career (18 walks in 30.2 innings) has to be the top developmental priority for Feliz right now.

4. MICHAEL MAIN, RHP, High A Bakersfield (4)

Now we're talking. Main improved to 4-1, 3.81 for the month with a solid five-inning effort on Friday, yielding one Inland Empire run on five hits and two walks, fanning two. The 20-year-old struggled so much in four April starts that his resilient five-start run in May has only resulted in an overall record of 4-4, 6.64. But he's obviously created something positive to build off of.

5. WILMER FONT, RHP, Low A Hickory (5)

Font gave up two runs over three innings on Sunday (his 19th birthday) and it was his worst outing out of 10 this year. In only three appearances has he registered fewer strikeouts than innings pitched, and his ERA for the season remains a tick under 2.00. Walks are still an issue (his 34 punchouts in 31.2 innings are offset by 23 free passes), but his stuff is going to play at any level. Fun fact: in 15 at-bats with runners in scoring position and two outs, opponents have zero base hits off of Font.

6. KASEY KIKER, LHP, Double-A Frisco (6)

Despite a poor outing on May 21, in which he yielded only three runs (two earned) but couldn't get out of the fourth inning due to a 24-pitch-per-inning pace, Kiker still holds the Texas League lead in strikeouts, fanning 47 in 42.2 innings of work. The 21-year-old lefthander is the Texas League's third-youngest pitcher and is limiting opponents to an anemic .184 batting average. Nobody in the major or minor leagues has hit as many batters as the 11 Kiker has drilled.

7. BLAKE BEAVAN, RHP, High A Bakersfield (12)

That's four straight quality starts for Beavan, by any definition. After sitting at 0-4, 7.88 through his first five Bakersfield starts, allowing Cal League batters to hit .310 off him, in the next four the big righthander has gone 3-0, 2.17, yielding just 25 hits (.236 opponents' average) and four walks in 29 innings while fanning 16. Sturdy.

8. ENGEL BELTRE, CF, High A Bakersfield (8)

Beltre has gone hitless only once in May, putting together a .305/.367/.427 month after a .178/.221/.267 April. A player who has always played with the type of flair you can't take your eyes off of, he's hitting .438/.500/.625 in the ninth inning this season.

9. WILFREDO BOSCAN, RHP, Low A Hickory (7)

The 19-year-old righthander missed five weeks with an oblique muscle strain but showed no rust in his return on Wednesday, scattering two singles and a walk in five innings to earn his third win in four starts. Boscan lowered his ERA to 0.40 in the process, and shaved his opponents' slash line down to a silly .104/.148/.156.

10. JULIO BORBON, CF, Triple-A Oklahoma City (9)

Borbon filled the box score on Wednesday, contributing a single, double, triple, walk, stolen base, two RBI, and a run scored to a 14-6 Oklahoma City win over Reno. In his last 14 games, the fleet center fielder is hitting .381/.409/.524, lifting his season numbers to .294/.347/.374. You'd like to see more than 12 walks in 187 at-bats from the leadoff candidate, but he's gone down on strikes only 15 times, seeing a 13-game strikeout-less streak come to an end on Saturday.

11. MAX RAMIREZ, C, Triple-A Oklahoma (10)

Come on, Max. A .234/.275/.328 April followed by what's now a .241/.279/.329 May? If Texas can get a big June out of the 24-year-old, a lifetime .311/.410/.512 damage machine coming into the season, he can still be a very important asset in July.

12. JOSE VALLEJO, 2B, Triple-A Oklahoma City (11)

Vallejo has cooled off over the last week but is still hitting .304/.360/.391 since his promotion to Oklahoma City four weeks ago. He's made only one error playing second base for the RedHawks, but has only stolen one base (after swiping 47 and 42 bases the last two seasons).

13. GUILLERMO MOSCOSO, RHP, Double-A Frisco (13)

Going into the ninth inning on Monday, Moscoso was shutting San Antonio out on two hits and no walks, striking out 11. It was the 25-year-old's strongest effort in a string of nothing but solid efforts since a disastrous 2.2-inning, eight-run appearance on April 19. Subtract that game, and Moscoso, who was half the Rangers' return from Detroit for catcher Gerald Laird, would have a 2009 mark of 3-0, 2.95.

14. OMAR POVEDA, RHP, Double-A Frisco (17)

If you need evidence that Poveda (5-3, 3.10) is commanding one of the system's best changeups again, just check the L/R splits: after left-handed hitters were more successful than righties against the Venezuelan righthander in 2008, he's back to baffling lefties in 2009, holding them to a .211/.258/.333 slash line (while righties are hitting .241/.331/.343). The 21-year-old threw the game of his life yesterday, shutting Tulsa out on three singles and two walks in what was the first complete game of his five-year career. He needed only 107 pitches and retired 15 straight Drillers at one point.

15. MANUEL PINA, C, Double-A Frisco (14)

After finishing April with the best batting average in the minor leagues and the Rangers' Minor League Player of the Month award, Pina has struggled in May, hitting just .209/.276/.299. He's mired currently in an 0-for-20 skid.

16. JAKE BRIGHAM, RHP, Low A Hickory (16)

Brigham bounced back from three subpar efforts with a dominant start on Monday, limiting Hagerstown to three singles and a walk in five innings of work, and setting eight Suns down on strikes. The 21-year-old is 2-2, 3.60 for the season, fanning 39 and walking 17 in 35 innings.

17. MITCH MORELAND, 1B-OF, Double-A Frisco (18)

Moreland kicked off his AA career in style, going 3 for 4 with a double in his Frisco debut on Wednesday, hitting third and scoring twice in a 5-0 RoughRiders win over Tulsa. Despite Justin Smoak's absence from the lineup, Moreland played right field, something he stands to do regularly in Frisco. He departs the Cal League leading the circuit with 19 doubles and sitting among the league leaders in just about every other hitting category as well, having hit .341/.421/.594 with eight home runs and 26 RBI in 43 Bakersfield games.

18. MICHAEL KIRKMAN, LHP, Double-A Frisco (19)

Kirkman's introduction to the Texas League was a little bumpier than Moreland's. The 22-year-old lefthander got the Frisco start on Sunday, and allowed three San Antonio runs on nine hits and five walks in five innings, fanning three. He'd put up a 54/18 strikeout-to-walk ratio in Bakersfield, where he went 4-1, 2.06 and departed the league as its ERA and strikeout leader.

19. KENNIL GOMEZ, RHP, High A Bakersfield (UR)

Gomez's season has been uncharacteristically uneven (2-3, 5.20) but he was outstanding on Monday, holding Inland Empire to one run on four hits and four walks in seven innings, fanning nine. In 45 Blaze innings, he's punched out 54 and walked 21, and in keeping with his history he's generating groundballs in bulk, coaxing 2.35 as many groundouts as flyouts.

20. ZACH PHILLIPS, High A Bakersfield (UR)

A wholesale shift to the bullpen has been a successful one for Phillips, who has stymied California League hitters in 11 relief appearances (two runs [0.95 ERA] on seven hits [.104 opponents' average] and two walks in 19 innings, with 22 strikeouts) with one less dominant start (three runs on five hits and two walks in five innings, fanning four) mixed in. His work against lefthanders (two hits and two walks in 37 at-bats, 17 strikeouts, .054/.103/.054 opponents' slash line) stands out among a group of southpaw relievers (A.J. Murray, Corey Young, Yoon-Hee Nam, Beau Jones, Ryan Falcon, Glenn Swanson) who have taken steps forward in 2009.

Off the list this week: A.J. Murray, Corey Young

Six pitchers to watch: Richard Bleier, Fabio Castillo, Doug Mathis, Yoon-Hee Nam, Matt Nevarez, Joe Wieland

Six hitters to watch: Mike Bianucci, Mauro Gomez, Matt Lawson, Erik Morrison, David Paisano, Tim Smith