Joe Nathan's illustrious career in Major League Baseball might be over.

The 40-year-old Detroit Tigers closer suffered a torn ulnar collateral ligament in his pitching elbow during a rehab appearance on Wednesday. The injury will require season-ending Tommy John surgery.

Nathan, who averaged 37 saves in seven seasons with the Twins (2004-2011), said he's going to approach his rehab as if his big-league career will resume, FOX Sports reports.

"I'm going to go at this 110 percent, just like I do anything, and I'm going into it with the goal of pitching again in the major leagues," he said. "If it doesn't work out that way, the surgery and the rehab will make my arm stronger for the rest of my life, but that's not how I'm thinking about it."

According to USA Today, this is the second UCL surgery Nathan will have, the success rate of which is much higher the second time around.

"I don't know if this is necessarily the last pitch he throws," Tigers manager Brad Ausmus said.

Nathan's 377 career saves are the most among active closers and the seventh-most in MLB history.