ARLINGTON -- The Rangers are switching Scott Feldman and Roy Oswalt in the rotation. Oswalt, who threw in the bullpen on Friday, is now scheduled to pitch on Monday against the Angels.

Feldman is being moved up and will pitch Sunday against the White Sox. The Rangers decided to give Oswalt an extra day of rest to recover from the tightness in his lower back.

"There's nothing wrong, we just decided to switch it and give Oswalt an extra day," Rangers manager Ron Washington said. "Feldman is good to go on Sunday."

Oswalt was scratched from his last start on Monday. He will be pitching on 12 days' rest when he takes the mound on Monday.

"I should be ready to go. I feel great," Oswalt said. "I could go tomorrow. I threw a bullpen today so I could throw either Sunday or Monday. They told me I was going to throw Monday. It doesn't really matter."

Oswalt improved to 3-1 in his last start July 17 against Oakland, giving up one run on three hits over 6 1/3 innings while striking out six and walking none during a 6-1 win over the A's. He has posted a 5.22 ERA and struck out 25 batters in 29 1/3 innings over five starts.

"My job is to eat up as many innings as I can," Oswalt said. "We've got some tremendous arms, some tremendous pitchers. Derek [Holland's] coming around. He threw really well his last start. [Yu] Darvish has been throwing great. [Matt] Harrison's been lights-out. You've got three guys that have been throwing great all year. All you try to do is continue that throughout the starting five."

Lowe to begin rehab assignment Saturday

ARLINGTON -- Rangers pitcher Mark Lowe will join first baseman Mitch Moreland at Double-A Frisco on Saturday night.

Lowe is scheduled to pitch one inning in his first outing on a medical rehabiltation assignment. He has been on the disabled list since June 26 with a strained intercostal muscle in his right rib cage and will likely need two outings before he is activated.

"He has been down a while and hasn't faced hitters," Rangers manager Ron Washington said. "I don't see how he can do one inning and come back."

Mitch Moreland, in the third game of his rehab assignment and first with Double-A Frisco, went 3-for-4 with a pair of doubles and four runs scored on Friday. He led off the bottom of the first with a double to center, had an RBI double to right in the next inning, and singled to left in the fourth before grounding out to second in the fifth inning and getting hit by a pitch during the seventh.

Moreland, who has been on the disabled list with a strained left hamstring, was 1-for-6 in two games for Triple-A Round Rock on Monday and Tuesday. He spent Wednesday and Thursday with his wife Susannah, who gave birth to their first child. Moreland is expected to play Friday and Saturday for Frisco and then the Rangers will decide if he's ready to come off the disabled list.

"We'll wait and see how his at-bats go," Washington said. "He can't go down there and do nothing, and then come back here and do nothing. We'll see how his at-bats go."

Napoli starts at DH after missing one game

ARLINGTON -- Mike Napoli missed Wednesday's win over the Red Sox with tightness in his left quad but was back in the lineup starting at designated hitter and batting seventh in Friday's series opener against the White Sox.

Napoli sustained the injury while running to first base in the third of inning of Tuesday's game when he grounded into a double play. He finished the game and drew walks in his next two plate appearances but did not advance to second base either time. Napoli has not run since then but is expected to catch the last two games of the series against the White Sox this weekend.

"I was running down the line and my quad just tightened up on me," Napoli said. "It's a little sore but I don't think it's really anything serious. I haven't run on it since. It doesn't bother me walking on it or anything. But I wasn't sprinting on my off-day. I was relaxing."

Manager Ron Washington said that had the Rangers not had an off-day before Friday's game, Napoli would have started at first base and Michael Young would have started at designated hitter. Now, Napoli will go three straight days without starting behind the plate.

"I'd rather have Napoli DH," Washington said. "He'll be back [at catcher] tomorrow and Sunday. If I had to make a choice between putting him at first or putting Michael at first, I think Michael is the better first baseman. Michael seems to be more engaged when I've got him on the field."

Worth noting

• Manager Ron Washington said the goal for Neftali Feliz is five innings and 80 pitches in his next rehab start for Triple-A Round Rock on Sunday night. Asked if Feliz could be activated after that, Washington said, "We'll just wait and see how the outing goes."

• Joe Nathan has been successful on 18 straight save opportunities. The single-season club record is 21, set by Francisco Cordero in 2004.

• Double-A Frisco outfielder Val Majewski was placed on the seven-day disabled list with a hamstring injury and Frisco right-hander Neil Ramirez was activated from the seven-day disabled list. Majewski has not played since July 22, while Ramirez last pitched July 17, sitting out with right shoulder soreness.