Manager Terry Collins said before the Mets faced Texas that they had recently noticed a drop-off in the crispness of some of his pitches.
Niese missed six weeks last season with a partial tear in his rotator cuff and was sidelined this spring with shoulder weakness, but Collins insists the team is just being cautious with its most consistent starter.
''There's no discomfort, no pain like last year,'' Collins said. ''You don't need radar guns to tell you there's something going on here.''
Niese agreed with the move because he's been having trouble for about six weeks, but said this break is nothing like his DL stint last year.
''It finally caught up with me,'' Niese said. ''It's something I can pitch through ... I think this is as good as any to take a break.''
The Mets recalled reliever Buddy Carlyle from Triple-A Las Vegas but he's likely a placeholder for starter Dillon Gee. The right-hander has been on the disabled list since May 11 because of a strained right lat muscle.
Gee has made three rehabilitation starts, and Collins said Gee's readiness to start in Niese's place Wednesday factored into the decision to DL Niese.
After the Mets' 8-4 win Sunday, Collins said Gee felt great after a bullpen session and he should start Wednesday.
With the All-Star break starting after games next Sunday, Niese should miss only one start.
The Mets hope the rest will help Niese have a strong second half in a similar fashion to his return from the DL last season. He came back on Aug 11 and went 5-2 with a 3.00 ERA the rest of the way.
''Last year when he rested his shoulder, the second half was huge,'' Collins said. ''His second half last year was outstanding, after we took time to get his strength back. I told him, 'You'll have 15 starts left, go win 10 of them.'''
Niese was slowed by shoulder trouble and elbow inflammation this spring. He didn't make his first start until April 6.
But he's been the team's most reliable starter this season, going 5-4 with a 2.96 ERA in 17 starts.
The left-hander was hit in the side by Alex Rios' liner in his start Friday. He told Collins he was fine, but was removed anyway without trying a warmup pitch. Collins, though, said this move was not related to that.