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6/12/2013 7:23 P.M. ET

Wheeler's pending arrival to set roster wheels in motion

NEW YORK -- With Zack Wheeler's promotion from Triple-A Las Vegas less than a week away, manager Terry Collins is nailing down a plan on how to manage the rotation with another starter on the roster.

Wheeler will pitch one game of the doubleheader in Atlanta on June 18. He'll be the 26th player on the roster that day, which is allowed after a rule change in the most recent Collective Bargaining Agreement. After that, though, the Mets will need to figure out who will lose his spot to make room for Wheeler.

It won't be anyone in the rotation just yet.

"He's not replacing anybody," Collins said. "What we're going to do, most likely, when Zack comes, [is go] with an extra starting pitcher for a turn so that everybody can stay in line."

Eventually, though, one starter will be sent to the bullpen.

As far as who will be sent to Las Vegas to clear a roster spot, Collins said that's a decision for general manager Sandy Alderson to make.

Wheeler has made 12 starts for Las Vegas, and has a 4-1 record, 4.14 ERA and 66 strikeouts in 63 innings.

And from the reports Collins has been getting, he's going to be even better with the Mets.

Scouts have said that Wheeler will likely improve at the Major League level. Collins said there are a couple of reasons that might factor into that, including Wheeler's focus starting to wane as he continues to overpower Minor League-level talent.

"There are guys that get bored, who know they belong at the next level," Collins said.

Collins added that pitchers can have more confidence in the Majors, knowing there are typically better fielders playing behind him. And in Wheeler's case, he won't be pitching in Las Vegas, where the dried-out field plays quick and grounders often scoot through the infield for hits.

Collins wants Wheeler to understand that he doesn't have to throw a no-hitter every time out, just pound the strike zone with quality pitches, and he'll get outs.

As Wheeler's promotion draws near, the anticipation continues to grow. Collins isn't exempt.

Said Collins: "I'm anxious to see him."

Buck struggling under weight of responsibility

NEW YORK -- Manager Terry Collins said that catcher John Buck's current struggles at the plate are a result of him trying to do too much. Buck is 18 for his last 103 at-bats dating back to May 3.

Buck has 11 home runs this season, but nine of them came in April, and he hasn't hit one since May 24.

Collins said Buck is trying to carry the team on his own with so many of his teammates struggling.

"I think John's just trying to step up and pick up that big load, because he did early," Collins said. "No one guy can do it by himself."

Chris Iseman and David Wilson are associate reporters for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.