Zimmermann, who turns 35 on May 23, pitched in just three games for the Detroit Tigers last season due to a forearm injury after going 1-13 with a 6.91 ERA in 2019. He was a two-time All-Star with the Washington Nationals, who selected him from Division III school Wisconsin-Stevens Point in the second round of the 2007 draft.
He described his injury as a "forearm flexor thing'' and returned to make three September appearances last year, going 0-0 with a 7.94 ERA. Zimmermann says he now is as healthy as he's been in a few years.
"If I didn't feel good or I didn't feel healthy, I was probably thinking about retiring,'' Zimmermann said. "But I started working out, started running, started throwing and doing everything I normally do. The body feels good and the mind is telling me to keep going. I'm going to definitely give it another year, and we'll see what happens after this year.''
Zimmermann went 70-50 with a 3.32 ERA with the Nationals from 2009 to 2015, and he finished seventh in the Cy Young Award voting in 2013 and fifth in 2014 while making the NL All-Star team both of those seasons.
He threw the first no-hitter in Nationals history when Washington beat the Miami Marlins 1-0 in the 2014 regular-season finale.
Zimmermann wasn't nearly as effective after moving to the American League, posting a 25-41 record with a 5.63 ERA for Detroit over the past five seasons.
"If I didn't have anything left, I probably would have retired and gone out on my own terms,'' Zimmermann said. "But my body and my mind tell me, 'You still have more left.' Obviously, I want to go out there and stay healthy. I know I can get guys out. It's definitely going to be nice getting back in the NL because I feel a lot more comfortable there than where I was.''