Matt Harvey, the 24-year-old right-hander who had emerged this season as one of the best pitchers in baseball, has suffered a partial tear of his ulnar collateral ligament in his right elbow, raising the prospect that he will now need Tommy John surgery and will not pitch again until 2015.

The disclosure of Harvey's injury came in a Monday afternoon news conference held by New York Mets general manager Sandy Alderson. It came two days after Harvey gave up a season-high 13 hits against the Detroit Tigers. After the game, Harvey spoke of general fatigue, which was attributed to the 178 innings he has pitched this season.

But Alderson said Harvey informed the Mets that he felt forearm tenderness, which led to Monday's MRI exam. Harvey has not yet been put on the disabled list, but that issue almost seems a technicality against the larger concern that he will need surgery and be shut down for an extended period.

"We're not going to do anything to jeopardize his future with the Mets," Alderson said.

Alderson said that Harvey had been receiving preventive elbow treatment since spring training, but that it was unclear when the forearm tenderness began. Harvey said he has not felt any elbow pain.

For the season, Harvey is 9-5 with a 2.27 earned run average and 191 strikeouts, which leads the National League. In July, he was the starting pitcher for the NL in the All-Star Game, which was held at Citi Field. The honor underscored the status that Harvey had quickly achieved in baseball.

But now his immediate future is in doubt, casting a demoralizing blow to a franchise that hoped to become a contender as early as next season with Harvey as the linchpin.

Harvey is a graduate of Fitch High School in Groton