Jay Bruce is returning to the New York Mets on a three-year, $39 million contract, and my initial reaction was: Why would the Mets want Bruce when they already have Yoenis Cespedes and Michael Conforto to play in the outfield corners?

So let’s figure this out.

First, the money is relatively low-risk and not ridiculous. It’s also not a bargain, as Bruce’s name recognition exceeds his actual value. While he has slugged 69 home runs the past two seasons -- 10th-most in the majors -- most of his value is wrapped up in those home runs as he was worth 0.6 WAR in 2016 and 2.9 in 2017. Due to his mediocre batting average and below-average walk rate, his on-base percentage over the past two seasons is .317, compared to a league-wide mark of .334 for right fielders. He’s a below-average baserunner and his defensive metrics have been all over the place, which is why his WAR was much higher in 2017.

For what’s it worth, he has rated well while with the Mets the past two seasons (plus-12 defensive runs saved over 1,151 innings), but poorly with the Reds and Indians (minus-17 DRS over 1,178 innings). I have no idea what to make of that; logically, it doesn’t make sense, so it could be just a weird sample-size thing, a reflection of the difficulty in grading defense, or some other factor. Ultimate Zone Rating, another metric, agreed that he was bad in 2016 (minus-8.9 runs) and better in 2017 (plus-1.8 runs). Anyway, we know Bruce isn’t fast and he won’t be getting faster in his 30s (the contract runs from his age-31 season through his age-33 season in 2020), so at best he’s an average defender now and probably slightly below moving forward.

With Bruce in right field and Cespedes in left, that slides Conforto over to center, where he did start 39 games last season. His sample size of 328 innings there isn’t enough to tell us much beyond that he wasn’t great when he was out there, but the Mets must have some comfort level in believing he won’t be a disaster in center. Note that Cespedes, who played some center in the past, didn’t play a single inning out there in 2017, so that doesn’t appear to be an option.

But there is some flexibility here. Conforto had surgery in September on his left (non-throwing) shoulder and he’ll be ready for the start of the season. In Juan Lagares, they have an elite defender, and they could end up platooning him with Conforto or Bruce given neither of those two have hit lefties:

Conforto vs. LHPs in his career: .180/.249/.329

Bruce, 2016-17: .222/.276/.422

Now, Conforto has just 177 career plate appearances against lefties, so we don’t know for sure that he can’t hit lefties. You’d like to see him get more opportunities before making that decision. Still, if the Mets want to go with a straight Lagares/Conforto platoon in center, it would be understandable. You could use Lagares in center based on whether it’s a ground ball or fly ball pitcher (although none of the Mets' starters were extreme fly ball pitchers in 2017).

Throw in Brandon Nimmo, and the Mets have plenty of depth now in the outfield. There’s nothing wrong with that, especially given that Conforto and Cespedes haven’t exactly been Cal Ripken Jr. throughout their careers. The other option is that Bruce could see some time at first base to give Dominic Smith more seasoning in the minors -- a good idea considering his struggles in his big league debut.

The Mets can’t stop at Bruce. They need to add a second baseman or third baseman (with Asdrubal Cabrera playing the other position). They’ve been linked to Todd Frazier and Mike Moustakas for third and Neil Walker for second. The closer we get to spring training, the more the prices should drop on those guys.

Of course, the ultimate key will be better run prevention. The Mets were next-to-last in the National League in runs allowed after posting an ugly 5.01 ERA. The problem wasn’t just Noah Syndergaard’s injury or Matt Harvey’s debacle of a season. The defense was awful, worst in the majors via Defensive Runs Saved with minus-70 runs. Signing Bruce and playing Conforto in center isn’t going to help that, which means the fate of the 2018 Mets will rest on the once-vaunted rotation returning to its not-so-long-ago glory.