McCarthy said he will wait and see if his sore right elbow is something more serious after relieving Jennings, who threw 2 2-3 scoreless innings in the Texas Rangers' 9-8 loss to the Milwaukee Brewers on Friday.
McCarthy, scheduled to throw two innings after Jennings did, pitched just one and felt soreness when he threw his third curveball of the day. He will be re-examined on Saturday.
"Hopefully, it's nothing too serious and it's something we can get past soon," McCarthy said. "But, it's not fun right now."
McCarthy, who went 5-10 with a 4.87 ERA in 23 games in his first season in Texas last year, has been delayed this spring because of the elbow.
"You get pretty sick of talking about yourself and your injury," said McCarthy, who spent two stints on the DL last season with a blister and a stress fracture in his right shoulder blade. "I'm not too worried, it's just annoying."
Jennings allowed just one hit in his second scoreless appearance this spring since signing a one-year deal with the Rangers following a year in Houston.
Jennings, the 2002 NL Rookie of the Year who was born in Dallas, was 2-9 with a career-worst 6.45 ERA in 19 games with the Astros. He missed three months because of elbow problems and needed season-ending surgery in August to repair a torn tendon.
"There's no pain whatsoever this year," Jennings said. "That's all I'm worried about right now."
Capuano was fine through two innings, but his problems began in the third after he allowed four straight singles, including a long at-bat with Frank Catalanotto that ended with Catalanotto hitting a slow bouncer through the infield.
Capuano then walked Michael Young before Hamilton's homer chased him.
"I don't want to say I got tired, I hate saying I get tired, but the ball was just up the last inning," Capuano said. "When I fell behind to Hamilton there, I just threw him way too good of a pitch to hit."
Brewers LF Ryan Braun hit a three-run homer in the fifth inning, his second home run in as many days. ... Rangers 3B Hank Blalock took batting practice and went through drills, but didn't play for the seventh straight game, the fourth since his vehicle was rear-ended while stopped at an intersection. He is expected to DH on Saturday. ... Brewers 1B Prince Fielder took batting practice, but did not play. Fielder, 2B Rickie Weeks and 3B Bill Hall are on a schedule of playing two days and working every third on individual defensive drills, Brewers manager Ned Yost said.