Zack Wheeler of the Mets stands on the mound in...

Zack Wheeler of the Mets stands on the mound in the second inning of a game against the Oakland Athletics at Citi Field on Wednesday, June 25, 2014. Credit: Jim McIsaac

Before a torn ulnar collateral ligament wiped out Zack Wheeler's season, the Mets worried about a different issue in his troublesome right elbow: a torn tendon.

The tendon tear, a source told Newsday, is what prompted Wheeler to undergo platelet-rich plasma therapy twice this offseason. Doctors hoped the treatment would speed up healing and allow Wheeler to keep pitching.

"They thought that the rest and the PRP would allow it to calm down," the source said. "And it didn't . . . For whatever reason, it didn't help, it didn't take."

Wheeler, 24, had been cleared to keep pitching last season despite chronic pain caused by what the team has been calling inflammation of the tendon, or tendinitis. According to a source, it turns out that the tendon was actually "a little bit torn."

Wheeler's elbow ligament, meanwhile, showed no signs of a tear until Saturday. That's when lingering pain prompted an MRI exam on Saturday.

On Wednesday, Wheeler was examined by team doctor David Altchek in New York. According to the source, Altchek confirmed a "pretty substantial" tear of Wheeler's UCL, which had been expected.

The examination also revealed more tearing in Wheeler’s tendon in addition to calcification in the elbow joint.

But the source said that neither issue fundamentally altered Wheeler's fate last season. Since doctors assured him that the injuries couldn't be made worse in any significant way, Wheeler was left to decide how much pain he could stand in order to keep pitching.

Still, the new revelations paint a clearer picture of the health woes that Wheeler endured to pitch a career-high 185 2/3 innings.