OAKLAND -- A pair of battered A's infielders gave the club what manager Bob Geren deemed "good news" on Tuesday.

First baseman Daric Barton and shortstop Cliff Pennington, who both exited Sunday's 8-3 loss to the Orioles with injuries, were back in the lineup for Oakland's first game against the visiting Yankees.

Barton, hit by a pitch above his right elbow by Baltimore starter Brian Matusz in the fourth inning on Sunday, chose to play on Tuesday despite healing from the contusion.

The infielder, who has started all 15 A's games this year, underwent X-rays on Sunday before having an MRI on Monday -- both of which came back negative.

Pennington, meanwhile, was the No. 9 hitter on Tuesday after exiting Sunday's game in the seventh inning. He underwent X-rays -- which came back negative -- near the area of his right hand and wrist after being stepped on while diving back to first base in the third inning.

Both Barton and Pennington were afforded the luxury of resting their respective injured bodies on Monday, as the team enjoyed its first off-day of the season.

After starting, Ellis exits with injury

OAKLAND -- Mark Ellis left Tuesday's A's game against the Yankees with a sore left hamstring -- the same injury that forced the Oakland second baseman to be sidelined the past seven games.

Ellis was 0-for-2 at the plate through five innings before being replaced by Adam Rosales at second base at the start of the sixth frame.

The 32-year-old Ellis was making his first start since April 11 at Anaheim, where he experienced hamstring soreness while running to first base on a grounder. He also missed a handful of Spring Training games with tightness in both hamstrings.

Back from DL, Cahill sent down

OAKLAND -- Trevor Cahill will have to wait a little while longer to build on a 2009 rookie season that saw him lead the A's staff in starts and innings pitched.

The right-hander, who made a rehab start for Triple-A Sacramento on Monday, was optioned on Tuesday and thus will continue his stay with the River Cats.

The move came immediately following Oakland's decision to reinstate Cahill from the 15-day disabled list, where he started the season due to a left shoulder stress reaction. Cahill was 1-1 with a 5.95 ERA in six games -- including four starts -- during Spring Training before revealing a neck injury that bothered him late last season.

In his first rehab outing, which came on Monday, Cahill allowed two unearned runs on two hits and three walks in 3 2/3 innings while being monitored on a limit of 60 pitches. Before the transaction news surfaced on Tuesday, Cahill said he'd continue building up his arm strength again by increasing his pitch count in increments of 20.

"I felt good," Cahill said. "I felt a little fatigued after I was done, but I know that's all part of getting my strength back."

The 22-year-old right-hander was very much in the mix for the No. 5 spot in the A's rotation throughout Spring Training until his injury surfaced -- news that played a role in the club's decision to go with lefty Gio Gonzalez.

"I'm happy with the five starters we have right now," manager Bob Geren said as Gonzalez, Tuesday's starter, prepared to take on the visiting Yankees. "This will allow Cahill to raise his game up a bit. He did a nice job for us last year."

Cahill spent the entire 2009 season in the A's starting rotation, posting a 10-13 record with a 4.63 ERA. He joined lefty Brett Anderson in making the jump from Double-A Midland to the big leagues, where he made 32 starts and compiled 178 2/3 innings.

Geren on Tuesday went through a to-do list of improvements Cahill can work on to earn another starting nod in green and gold, chief among them being a better "overall strike percentage."

"That will obviously reduce the number of walks," the A's skipper said. "He'll continue to work on his breaking ball, and if he can combine all those improvements, it won't take him long to get back here."

Wuertz nears end of rehab stint

OAKLAND -- A's right-hander Michael Wuertz is scheduled to make his third rehab appearance with Triple-A Sacramento on Wednesday, when the River Cats are slated for an unusual 11:30 a.m. PT start.

Wuertz, who was placed on the 15-day disabled list on April 3 with right shoulder tendinitis, has allowed just two hits and a walk with one strikeout in two innings of rehab work so far.

Following a 2009 season in which he made a team-leading 74 appearances while compiling a 2.63 ERA, Wuertz appeared in just two Spring Training games due to the sore shoulder.

The 31-year-old Wuertz is in the midst of his first career stint on the DL and said on Tuesday that he may undergo one more rehab outing following Wednesday's outing, depending on the results.

Worth noting

Daric Barton has reached base safely via a hit, walk or hit-by-pitch in 14 of his 15 games this season. ... Kurt Suzuki has an 11-game hitting streak against the Yankees dating back to July 18, 2008, a span during which the A's catcher is 20-for-47. He is a career .403 hitter against the Yankees -- his best mark against any American League team. ... Ryan Sweeney had his 13-game hitting streak snapped on Tuesday. The streak matched a career high and is tied for the second-longest season-opening streak in Oakland history. ... Dallas McPherson, who had 12 RBIs in his first seven games with Triple-A Sacramento, is on the disabled list with a strained hamstring.