DETROIT (AP) — This is the final year of Jordan Zimmermann's contract with Detroit — and after battling injuries and ineffectiveness through most of his tenure with the Tigers, this is also his last chance to make a good impression before free agency arrives again.And now that opportunity may be gone.The Tigers put Zimmermann on the 45-day injured list last weekend because of a right forearm strain, and in this shortened season, that means he won't pitch much — if at all.Zimmermann went 1-13 with a 6.91 ERA last year. He has a 5.61 ERA in four seasons with Detroit. If he was going to be any kind of significant target on the free agent market for 2021, he needed to show he could stay healthy and effective, but now his best-case scenario is to return to the mound at the very end of the season.“There's a lot of innings on that arm, and he's had to deal with a lot of things,” Detroit manager Ron Gardenhire said. "He's going to try to get himself better, and somewhere down the road, maybe at the end, we'll get him back out there. I think he wants to show people he can still pitch.”At this point, it's still an open question whether baseball will be able to finish its 60-game season, so 2021 seems like a secondary concern. But it's not too early to think about what the future could hold for some.Players like George Springer figure to be well-valued in free agency no matter what happens this year, but for others, the 2020 season could be crucial. Here are a few more players who might be free agents after this season — and who could use a good showing over these 60 games.JAKE ARRIETA, PHILLIESThe 2015 National League Cy Young Award winner joined the Phillies before the 2018 season, agreeing to a three-year contract that includes team options for 2021 and ’22. Philadelphia may need to see more than Arrieta showed last year, when he went 8-8 with a 4.64 ERA before having surgery to remove a bone spur from his right elbow.ALEX GORDON, ROYALSGordon has been with Kansas City his whole career, but he's back with the Royals on just a one-year contract at age 36. Five years after a World Series title, Kansas City is back in a rebuilding mode. Gordon said a few months ago he would take things year by year, but he appreciated the significance of playing for only one team.DIDI GREGORIUS, PHILLIESGregorius played well while succeeding Derek Jeter at shortstop for the Yankees, but he was out until June last year following Tommy John surgery. He played 82 games in 2019, hitting .238 with 16 home runs for New York before signing a one-year deal with Philadelphia.COREY KLUBER, RANGERSAfter three straight seasons of at least 18 wins, Kluber was limited to seven starts last year because of a broken arm. He was traded from Cleveland to Texas, and the Rangers will have a decision to make after this season. They have a $14 million team option to keep Kluber in 2021. The right-hander turned 34 in April.RICK PORCELLO, METSThe New Jersey native welcomed the chance to play close to home when he joined the Mets in the offseason, but the 31-year-old right-hander has only a one-year deal with New York. Porcello posted a 5.52 ERA with Boston last season.TAIJUAN WALKER, MARINERSWalker signed a one-year deal with Seattle after missing almost all of 2019 following Tommy John surgery. He returned to the majors on the final day of the regular season, throwing a scoreless inning for Arizona against San Diego.___Follow Noah Trister at https://twitter.com/noahtrister___More AP MLB: https://apnews.com/MLB and https://twitter.com/AP_Sports