The left-hander entered Saturday tied for the American League lead with nine wins and will attempt to continue his recent hot streak on Sunday night, when the Rangers host the Rockies in the rubber game of a three-game set. Colorado will send Alex White (2-5, 6.06 ERA) to the mound as it tries to avoid a sixth straight series loss.
Harrison (9-3, 3.41) has the chance to help the AL West-leading Rangers rebound from seeing their seven-game win streak snapped in Saturday's 11-7 defeat.
Harrison's ERA is nearly identical to his 2011 mark of 3.39, but manager Ron Washington believes the 26-year-old is more mature and consistent this season. Harrison is 5-0 with a 1.43 ERA in his last six starts and 6-1 with a 2.45 ERA since consecutive rough outings on April 27 and May 2.
"I think the biggest thing is experience from last year as a starter," Harrison said. "I had two games earlier in the year that were bad starts after the three good starts. I learned a lot from those starts and why I struggled in those games. I was able to figure it out."
On Monday, Harrison held the Padres to one run on six hits in six innings, improving to 2-0 with a 0.40 ERA in three Interleague games this season.
"I found myself getting in a groove with my tempo and pounding the strike zone," said Harrison, who is pitching Sunday on five days' rest. "Hopefully, I can just continue that."
White is 0-2 with a 7.24 ERA in his last three starts. He gave up five earned runs in 3 2/3 innings on Wednesday against the Phillies before reaching the 75-pitch limit that goes with Colorado's new four-man rotation.
"Alex was just so-so," manager Jim Tracy said after the game. "His command was erratic."
Rockies: Offense behind the plate
Even with veteran Ramon Hernandez on the disabled list, the Rockies have not lacked production from their catchers of late.
Rookie Wilin Rosario is batting .435 (10-for-23) with two home runs and seven RBIs during a six-game hitting streak. He rested on Sunday following a 3-for-4 effort on Saturday, but Wil Nieves picked up the slack by smacking a two-run homer and going 2-for-4.
Nieves is batting .357 since his May 25 callup from Triple-A Colorado Springs, and any offense he provides is a bonus for Tracy.
"Wil Nieves is in the big leagues and has been in the big leagues not because of anybody sitting around on a day-in, day-out basis and raving about his offensive prowess," Tracy said. "It's moreso his capability of taking a pitcher with whatever he has on a given day and trying to get that out of him."
The Rockies' win on Saturday was their first in 11 games this season against an AL West team. They are now 2-12 in Interleague Play, with a team ERA of 6.53.
Rangers: Going through a rough patch
Mike Napoli went 1-for-3 with a home run on Friday and 2-for-5 with a double on Saturday following a 2-for-29 stretch over his previous nine games.
"I'm hoping it's going to turn around," Napoli said. "I'm working at it, I'm working in the cage, doing everything I can. It's basically getting comfortable at the plate and seeing the ball like I was before."
Even after plating seven runs on Saturday, the Rangers are averaging 4.3 per game in June, compared with 5.4 in April and 5.9 in May.
The only Rangers batter with experience against White is infielder Alberto Gonzalez, who is 0-for-2. Marco Scutaro, Michael Cuddyer and Carlos Gonzalez have the Rockies' 23 plate appearances against Harrison, combining for a 1.099 OPS.
Sunday's game is nearing a sellout, with the Rangers revealing that less than 100 reserved seats as well as scattered singles and obstructed-view seats remain.