Over the last several years, the opt-out clause has become a major factor on the free agent market. Want to sign a big free agent? Okay, but you're not only going to have to pay him handsomely, you're also going to have to give him an opt-out clause so he could potentially land an even bigger contract at some point. They come with the territory now.

The opt-out clause has been around for a while now -- J.D. Drew opted out of his contract with the Dodgers following the 2006 season, then signed with the Red Sox -- though they really became en vogue when Alex Rodriguez opted out of his contract in the middle of the 2007 World Series. After that, every elite free agent sought an opt-out. Nowadays even mid-range free agents are getting them.

This coming offseason six players, including one 2017 All-Star, will be able to opt out of their contracts and re-enter free agency. Will they actually exercise the opt-out clause? That's not quite as clear. Here are the six looming opt-out decisions.

Wei-Yin Chen SP / Marlins
Remaining Contract: Three years, $52 million

Marlins lefty Wei-Yin Chen seems like an easy "no." He figures to pass on the opt-out and collect the $52 million from 2018-20. Chen had a 4.96 ERA (80 ERA+) in 22 starts and 123 1/3 innings last year, and this year he threw 27 innings in five starts with a 4.33 ERA (97 ERA+) before being shut down with a partially torn ligament in his elbow.

Chen will begin a minor league rehab assignment Tuesday according to Tim Healey of the Sun Sentinel, so he figures to be back on a big league mound at some point in September. That should give him three, maybe four starts to strut his stuff for scouts before the opt-out decision. It's hard to think Chen can do enough in those few starts to convince teams he's worth more than $52 million over the next few years, especially given the elbow injury.