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7/31/2013 2:30 P.M. ET

Quentin exits with knee injury, won't play in finale

SAN DIEGO -- Padres left fielder Carlos Quentin left Tuesday's game against the Reds after "tweaking his right knee," according to the team, and San Diego manager Bud Black said he won't play on Wednesday.

Quentin was hitless in his only two plate appearances Tuesday at Petco Park before he was replaced in left field by Jesus Guzman prior to the sixth inning.

Quentin entered Tuesday's game with four home runs and a team-best 20 RBIs in July.

He felt some discomfort in his knee late in Sunday's victory over the D-backs in Phoenix and then didn't appear in Monday's victory over the Reds.

Since Quentin won't play in Wednesday's series finale, he'll get two full days of rest with Thursday's off-day before the team opens a three-game series Friday against the Yankees at home.

"The knee was tweaked in Arizona, he didn't play Monday and took another swing today that lit it up," Black said. "Hopefully, he'll be back in the lineup on Friday."

It was last October, right after the end of the regular season, when Quentin had arthroscopic surgery on his right knee. His participation in Spring Training was slowed after the surgery, and he appeared in only four games and had 14 at-bats.

After a slow start -- Quentin hit .239 in April and .191 in May -- he adjusted his stance, standing more upright in order to take stress off his knees. He then hit .366 in June before continuing his productivity this month.

Gyorko back in lineup after working on swing

SAN DIEGO -- Rookie second baseman Jedd Gyorko returned to the Padres' starting lineup Tuesday after not playing in each of the last two games.

That doesn't mean that Gyorko, who has scuffled at the plate of late, has been sitting around gathering dust.

"I've been in the cage a lot," Gyorko said. "I've been working these last couple of days on getting back to a good routine and a good rhythm at the plate."

Gyorko entered Tuesday's game against the Reds with four hits in his first 43 at-bats since coming off of the disabled list on July 12. He previously missed 30 games with a strained right groin.

Gyorko has 13 strikeouts in those 43 at-bats and had four in his last game Saturday against the D-backs. That's not the kind of hitter he is, Gyorko said.

"I was swinging at bad pitches, pitches I wouldn't normally swing at," Gyorko said. "When you do that, you're going to get yourself into trouble. You can't press to get a bunch of hits in one at-bat. You have to take it one at-bat at a time and get back to what got me here.

"I need to get a good pitch that I can control and put a good swing on it."

Extended rehab assignment in store for Maybin

SAN DIEGO -- Padres outfielder Cameron Maybin will begin a rehab assignment with Triple-A Tucson on Tuesday. He has been on the disabled list since June 12, retroactive to June 10, after damaging a ligament in his left knee.

Maybin's rehab assignment isn't expected to be brief. He's had two injuries that have limited him to just 14 games and 51 at-bats this season.

Maybin first landed on the disabled list on April 17 (right wrist impingement) and it cost him 45 games. Maybin returned for a four-game series with the Rockies, but he landed on his knee while attempting to catch a fly ball on June 9 and hasn't played since.

"He's got to get his legs underneath him and he's got to feel really good about where he is physically coming off this knee injury," said Padres manager Bud Black. "He's got to feel good about playing and doing everything a player needs to do to perform."

Black even likened Maybin's rehab assignment to a player going through a Spring Training before the start of the season. The 26-year-old is expected to gradually progress in innings and at-bats and spend some time at designated hitter and center field.

"This won't be a week-to-10-day thing," Black said. "It's going to be long ... to make sure that he feels confident about the knee, where it's tested.

"At the end of this assignment, he'll be playing consecutive games and playing nine innings and being Cam Maybin."

With O'Sullivan on paternity list, Mikolas called up

SAN DIEGO -- Sean O'Sullivan started Monday's game against the Reds knowing his wife, Sabrina, was due to have the couple's first child.

Padres manager Bud Black said he doesn't doubt that it likely crossed O'Sullivan's mind during the start, but O'Sullivan didn't seem too distracted. Even though he struggled with his command and issued five walks, he held the Reds to one run on five hits in six innings.

"Whenever I get on the field or step in the locker room, I think it's pretty easy to take outside life, leave it at the doors and pick it up as you walk out," O'Sullivan said after his start.

Sabrina went into labor on Tuesday, so the Padres placed O'Sullivan on paternity leave.

"There's probably a part of him where it was probably sort of cool, knowing that he was pitching the day before his son was going to be born," Black said.

Paternity leave allows a player to miss no more than three games. To replace him on the roster, the Padres have recalled reliever Miles Mikolas. In 44 games at Tucson this year, he is 3-1 with 21 saves and a 2.86 ERA.

His time in the Majors this season has been a bit unusual. Mikolas is making his fourth stint with the Padres this season, but he's only made one appearance.

Mikolas pitched a scoreless ninth inning against the Giants on July 11 before being optioned back to Triple-A the following day, then was recalled on July 21, but didn't make an appearance before being optioned back down the next day. The first time Mikolas was recalled was on June 23, but he did not make an appearance.

"Just like any relief pitcher, there's times where maybe you don't throw for three or four days and then maybe you're throwing three or four times in five days," Mikolas said. "So I've been throwing a lot [at Tucson] so it doesn't really mess up a rhythm as a reliever too much, because you're always on call."

Short hops

• One day before the non-waiver Trade Deadline, Padres third baseman Chase Headley wasn't in the starting lineup -- which might have raised more than just a few eyebrows had this happened a year earlier when he was rumored to be heading elsewhere in a trade. Not this time, though.

"He's not going to start, but he might play," said Padres manager Bud Black of Headley. "He's played in 11 straight games. I thought it was a good night to give him [rest]."

Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. Jamal Collier is an associate for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.