Kuo said he had "a little soreness in the back of the shoulder" and was scheduled to have an examination that would likely include an MRI.
"I just wasn't comfortable," Kuo said about his time on the mound Wednesday night, when he took over for scheduled starter Brad Penny, who reported stiffness in the front of his throwing shoulder.
Kuo said he also didn't feel right in his previous start five days earlier against Boston, when he allowed three home runs in a game that was rained out after 2 1/3 innings.
Kuo had no command against the Mets, walking four with four wild pitches in only three innings. For the spring, he has allowed 10 walks in nine innings with a deceptive 3.00 ERA. But add in the stats washed away from his previous start with Boston and he has a 6.35 ERA, 11 walks and 11 strikeouts in 11 1/3 innings, four homers, four wild pitches and a hit batter.
He did not participate in Thursday morning stretching and did not play catch with the other pitchers, instead spending the pregame taking treatment.
The good and bad news about the shoulder discomfort for Kuo is that it's not his elbow, which has undergone two Tommy John elbow reconstructions and has always had the organization uneasy about his durability.
Kuo came into Spring Training the apparent preferred choice in the fifth-starter competition because he is a rare hard-throwing left-hander who is effective against right-handed hitters. But he hasn't looked anything close to the Kuo that won a roster spot last spring, when in 12 innings, he allowed one run, struck out 14 and walked only one.
Fifth-starter update: The club was already planning to go with four starters the first time through the rotation, and with the way its fifth-starter contenders have pitched lately, maybe nobody will win the job.
Brett Tomko gave it up Thursday, charged with six runs in four innings. He allowed six extra-base hits, including a pair of home runs to Nick Markakis.
"I just left too many pitches up," said Tomko. "You can't do that when the wind is blowing out."
Tomko's ERA soared to 5.14 and he was followed to the mound by long-shot candidate Joe Mays, who allowed two runs in three innings as his ERA climbed to 4.85. With Kuo realistically at 6.35 and Mark Hendrickson at 5.40, Chad Billingsley's 0.96 is looking pretty good.
Nonetheless, manager Grady Little said he still plans to start the season with Billingsley in the bullpen.
"At least, initially," Little qualified.
"You're always on the lookout for someone to separate themselves from the pack, but the pack is all staying together."
Another loss: The 8-0 loss to Baltimore ran the Dodgers' losing streak to five, during which they've been outscored, 41-3, with three shutouts.
"We're not real concerned with spring games," said Little. "Our No. 1 concern is to get healthy."
Penny update: Penny was able to play catch with the other pitchers Thursday with no discomfort and plans to have a bullpen session Friday. If that goes well, he will start Monday.
Extra swings: Utilitymen Marlon Anderson and Ramon Martinez, with virtually guaranteed roster spots, led off every inning in a Minor League game.
Injury update: After club officials originally said Tony Abreu's bone bruise, suffered Saturday, would take two-to-four weeks to heal, the Dodgers miraculously announced Thursday the infielder was fully healed.
Abreu is ticketed to start the season playing second base for Triple-A Las Vegas, but he's had an impressive spring and could get a call-up to the Major Leagues any time.
Nomar volunteers: First baseman Nomar Garciaparra filmed a public service announcement to help promote youth volunteerism. The PSA, which has been organized by Volunteers of America and the Major League Baseball Players Association, also features Minnesota's Joe Mauer and New York's Carlos Delgado. During the offseason, Garciaparra and his wife, former soccer star Mia Hamm, launched their own charitable foundation called the 9-to-5 fund, which is named after their respective uniform numbers and will benefit Children's Hospital in Los Angeles in the fight against cancer.
Coming up: Derek Lowe starts and Joe Beimel will pitch on consecutive days for the first time this spring when the Dodgers travel to Jupiter to play the Marlins on Friday.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.