5 best candidates to call up when rosters expand in September

3) NY Mets need to figure out if David Peterson can pitch in relief

The Mets need to know what they can or cannot get out of David Peterson this year in a relief role. The lefty situation in the bullpen remains in question even with Joely Rodriguez not being a complete disaster. Peterson hasn’t been solid as a reliever but it would make a lot of sense for them to convert him into this role for a postseason run.

Right now, it makes sense to keep Peterson stretched out. He, along with Trevor Williams, is the best sixth starter the team could ask for. With the Mets planning to use Megill exclusively in relief if and when he returns, they could use the starting pitcher depth Peterson provides.

It’s very unlikely we see the Mets immediately promote Peterson on September 1. However, later in the year as things wind down, they may also use him as a two or three inning option in preparation for the postseason. It wouldn’t be so ridiculous for him to have a multi-inning role in October when starting pitchers tend to get an early hook.

With the two extra roster spots, one of them will fall to a different pitcher at least to start. By the time things wrap up, it would be important to understand whether Peterson is capable of giving them big outs late in a game.