CHICAGO (AP) Michael Conforto is hoping a short stay in Las Vegas turns into a strong finish with the New York Mets.

Conforto rejoined the Mets before the start of a three-game series against the NL Central-leading Chicago Cubs. The 10th overall pick in the 2014 draft was recalled when Brandon Nimmo, another young outfielder, was optioned to Triple-A Las Vegas after Sunday's 5-0 win at Philadelphia.

Also Monday, Mets right-hander Matt Harvey had season-ending thoracic outlet surgery in St. Louis. Harvey finishes the year with a 4-10 record and a 4.86 ERA after going 13-8 with a 2.71 ERA in 2015.

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The 23-year-old Conforto made his major league debut last year and hit .270 with nine homers and 26 RBIs in 56 games, helping the Mets win the NL East and make it all the way to the World Series. He then homered twice in Game 4 against Kansas City.

Conforto was expected to be a key contributor this year and got off to a nice start. But he was sent down on June 25 after a prolonged slump.

''It was a very productive couple of weeks, 16 games or so,'' Conforto said. ''I think there was a period of obviously being upset and you've got to go through that. As soon as I turned it into an opportunity to work on some things, to get some things done and take a look at what happened over the course of the prior couple months, I think I really look a couple big steps forward.''

Conforto hit .344 with three homers in 16 games with Las Vegas, earning a quick return to the majors.

''They said he was swinging great and the powers that be said it was time,'' Mets manager Terry Collins said.

Collins mentioned Conforto, Juan Lagares and Curtis Granderson as possible options in center after Yoenis Cespedes told reporters over the weekend he would prefer to stay in left for the rest of the year. Cespedes, who had a team-high 21 homers and 52 RBIs coming into the day, has been hampered recently by a strained right quadriceps.

Cespedes was in left for the series opener against the Cubs. Collins said he would be in center on Tuesday, but sounded as if he planned to keep him in left for most of the remaining part of the season.

''We've got to keep him in the lineup,'' Collins said. ''I think we're taxing his body pretty heavily by putting him into center field. We need him to hit and we need him to hit a lot. I just think if he's in left field, where he's comfortable and where's there's not as much emphasis on the defensive side, that he'll go back and do what we hope he can do and that's being a big production guy.''

Conforto said he thinks his last game in center was in college at Oregon State. But he said he was ready to play wherever Collins puts him.

''We had a conversation today about that,'' Conforto said. ''I know I haven't played there in pro ball. But if the team needs me there, I'm going to do whatever I can to prepare myself to play as well as I can there.''

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AP freelance reporter Mike Cranston contributed to this report.

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Jay Cohen can be reached at http://www.twitter.com/jcohenap