SAN DIEGO -- No longer fearful of significant structural damage in his left arm, Steven Matz learned Monday that he has avoided the worst. Tests on Matz’s arm confirmed that he is dealing with a nerve issue, but nothing involving his muscles or ligaments. Matz will miss a start and could land briefly on the injured list, but should return to the Mets before long.

The Mets placed Jason Vargas on the 10-day IL with a left hamstring injury, while Matz received an injection of cortisone and lidocaine but avoided the IL -- for now. The Mets aren't placing Matz there because they believe there is a chance he can start this weekend against the Marlins, or May 14 in Washington. (Matz last pitched Friday in Milwaukee, but pinch-hit the following day, limiting how long the Mets can backdate an IL stint.)

In addition to those moves, the Mets activated Justin Wilson from the 10-day IL and optioned Tim Peterson to Triple-A Syracuse.

Amidst that flurry of transactions, the team’s most pressing issue is who will start Wednesday in Matz’s place. Corey Oswalt, who was called up Monday to take Vargas' spot on the roster, is an option to make that start, as is trade acquisition Wilmer Font -- a reliever who will join the team Tuesday. Manager Mickey Callaway also mentioned Seth Lugo, Robert Gsellman and Drew Gagnon as options.

“Right now, we’re just waiting and seeing,” Callaway said Monday. “We’re going to get through these next two games and then make that decision.”

Matz, 27, returned to New York last weekend to have his left forearm examined, approximately two weeks after he first began feeling discomfort in that area. When he said something to team officials on Sunday, the club decided to send him for tests. Matz owns a 3.86 ERA, with much of the damage coming in one eight-run outing in Philadelphia last month. Without that start on his ledger, Matz would have a 2.31 ERA.

Vargas, 36, departed his last start in Milwaukee after only 50 pitches Sunday due to mild hamstring tightness. The injury occurred just as he was starting to thrive, with a 3.00 ERA and a .188 opponents’ batting average in his last four starts.

“He came in today a lot better than we would have expected,” Callaway said. “We’ll just have to wait and see. It’s still a hamstring. … It’s just too soon to speculate.”

Oswalt last pitched Wednesday for Syracuse, and can help the Mets either as a spot starter or in the bullpen. He has a 3.06 ERA in three starts at Syracuse, but a 12.15 mark in three Major League relief appearances. For Oswalt, the timing was perfect; he grew up in San Diego, and was able to invite his family to Monday’s game.

Wilson had been on the injured list since April 22 due to left elbow soreness, but threw multiple bullpen sessions last week and felt no pain. He carried a 3.24 ERA into Monday’s game in his first season with the Mets.