DeRosa, who signed a two-year, $12 million contract with San Francisco, hopes that the feeling will return in his fingers after a few days of rest. The infielder-outfielder consided it possible that the numbness is unrelated to his ligament damage, which isn't causing him discomfort.
"I can honestly say I'm not in agony," DeRosa said.
DeRosa, who underwent surgery last Oct. 26 to repair a torn tendon sheath in his wrist, said that he would consider another procedure.
"I'm not going to stink all year," he said. "... I'm doing myself and the team a disservice."
DeRosa thought he began sensing the numbness two or three weeks ago, which might coincide with an April 24 game against St. Louis in which he was hit twice by Adam Wainright pitches.
"I feel like my bottom hand's underwater. I don't have much feeling in my bottom two fingers," said DeRosa, a right-handed batter.
Manager Bruce Bochy theorized that DeRosa might have aggravated the injury with the countless extra rounds of batting practice he has taken.
"He's a tough guy," Bochy said. "He's a football player. He was trying to play through this."
DeRosa last played Saturday, when he went 0-for-5 at New York and didn't hit the ball out of the infield in three at-bats against Mets starter Johan Santana.
"It came to a full head in my second at-bat," DeRosa recalled. "[Santana's] throwing 88, 89 [mph] and I was sitting on a middle-in fastball. It was there on a tee. I went to move on it. When it came out of his hand, I [said], 'This is a bare minimum double to left-center.' The next thing I know, it's a weak popup to second base."
Playing for the St. Louis Cardinals, DeRosa sprained his left wrist last July 1 against the Giants while flailing at a Randy Johnson pitch. He played most of the rest of the season but batted only .228 with 10 home runs and 28 RBIs in 68 games for St. Louis, to where he was traded after hitting .270 with 13 homers and 50 RBIs in 71 games with Cleveland.
DeRosa nevertheless was among the most highly sought free agents on the market. But his struggles in St. Louis, combined with what he considered to be a subpar Spring Training performance (.255, one home run, two doubles, six RBIs) and his near-powerless start this year, prompted him to see doctors Tuesday.
His suspicions were initially raised when he began taking light batting practice before Spring Training and didn't feel quite right. But he figured that was part of the recovery process.
"The sample size is too large now," DeRosa said. "You're not a lifetime, .280, .275 hitter and then all of a sudden you hit .190."