NEW YORK (AP) All of a sudden, the New York Mets face this sobering uncertainty: Matt Harvey might never be a healthy ace again.
The struggling star has symptoms consistent with thoracic outlet syndrome and could require season-ending surgery to treat a serious condition that has jeopardized the careers of other major league pitchers.
General manager Sandy Alderson announced the unusual diagnosis Thursday after Harvey was examined in St. Louis by a specialist, Dr. Robert Thompson. Alderson said a decision on surgery is expected in the next few days before the All-Star break.
''I think you can bounce back from it, but everybody's different, as we know, anytime you have surgery. So there's a level of concern,'' Mets manager Terry Collins said. ''But certainly, you can't be very excited about it. You just don't know.''
Thoracic outlet syndrome is a condition caused by the compression of nerves, blood vessels or both in the area between the neck and armpit. After his start Monday, the 27-year-old Harvey complained of some common symptoms, which include numbness in fingers and shoulder discomfort.
The former ace was seen by Mets doctors, referred to Thompson for further examination and placed on the 15-day disabled list Wednesday, retroactive to Tuesday.
''His arm just felt like it was dead,'' Collins said.
Another temporary treatment option is a ''nerve-block injection'' that might help Harvey return to the mound fairly quickly, but surgery is probably inevitable and the operation usually requires a four-month recovery period, Alderson said.
Thompson would likely perform the procedure, the GM added. Surgery sometimes involves the removal of a rib.
Other big league pitchers have been treated for TOS with inconsistent results and varying degrees of success, including Josh Beckett, Chris Carpenter, Jaime Garcia, Matt Harrison, Shaun Marcum and Chris Young.
Thompson removed one of Young's ribs in a 2013 operation that helped the right-hander make a successful comeback as a major league starter.
''Again, anytime that you introduce a significant surgery of this type, I think you have to be cautious about what will happen,'' Alderson said. ''But at the same time, I fully expect that Matt will be back and ready to go in 2017.''
Harvey, who missed the 2014 season following Tommy John surgery on his elbow, is 4-10 in 17 starts with a 4.86 ERA - 80th among 99 qualifying pitchers in the majors.
He had been scheduled to start Saturday night at Citi Field against Max Scherzer and the NL East-leading Washington Nationals. Right-hander Logan Verrett will pitch in Harvey's place and could get a chance to hold down that spot in the rotation.
Verrett is 3-5 with a 4.01 ERA in 23 appearances this season, including five starts.
''We'll evaluate it, but right now he'd be the guy we would lean toward,'' Collins said. ''Logan's got some big shoes to fill.''
Complicating matters for a suddenly fragile Mets rotation, right-hander Zack Wheeler has had several setbacks in his recovery from Tommy John surgery this year. The team initially targeted the All-Star break for his return, but Wheeler hasn't even thrown off a mound yet and there's no longer a timetable for his expected progress.
''We have no idea when he's coming,'' Collins said. ''It's another huge setback.''
Alderson said he is ''confident, not certain'' that Wheeler will be back this season.
The defending NL champions trail Washington by three games following a 9-7 victory in the opener of their four-game series Thursday night.
Harvey has given up 111 hits in 92 2/3 innings, with 76 strikeouts and 24 walks. He hasn't won since May 30, but he and the team had insisted all season he was healthy.
The Mets reiterated Thursday that the right-hander didn't mention any symptoms until after Monday's outing, when he was tagged by Miami for six runs - five earned - and 11 hits over 3 2/3 innings before New York rallied from a 6-0 deficit to win.
For the Mets, the news means two of the team's top stars have developed career-threatening health conditions in less than 14 months.
Third baseman David Wright was diagnosed with spinal stenosis last year and missed more than four months. The 33-year-old captain has been sidelined again since late May and is expected to miss the rest of the season following neck surgery to repair a herniated disk.
''I don't want it to sound like woe is me - but woe is us,'' Collins said.
Selected seventh overall by the Mets in the 2010 amateur draft out of North Carolina, Harvey blossomed into one of baseball's best pitchers three years later and started the 2013 All-Star Game on his home mound at Citi Field.
He returned from Tommy John surgery last year and went 13-8 with a 2.71 ERA in 29 starts covering a career-high 189 1/3 innings.
Late in the season, agent Scott Boras said doctors recommended that Harvey be limited to approximately 180 innings in his first year back. At first, the pitcher was noncommittal about going beyond that total - generating a firestorm in New York with the Mets in the middle of a playoff race.
Soon after, he announced he planned to pitch in October.
Harvey threw an additional 26 2/3 innings in the postseason, going 2-0 in four outings while helping the Mets to their first pennant in 15 years.
He was working on a shutout in Game 5 of the World Series against Kansas City when he pushed to pitch the ninth inning and talked Collins into it. Given a chance to go back out to the mound, Harvey faltered and the Royals rallied to win the championship.