Filling in for injured John Maine, Nieve has yielded three runs in two outings against the Rays and Yankees -- the highest-scoring teams in baseball.
"Oh, it's been a tremendous surprise. Obviously, a pleasant one. His history wouldn't have indicated he would be this good," Mets manager Jerry Manuel said.
David Wright added an RBI double and Daniel Murphy had three hits for the Mets, who opened a 10-game homestand by improving to 6-10 in June. Francisco Rodriguez rebounded from a blown save with a perfect ninth inning.
In the first meeting between these teams since 2001, the Rays mustered little offense. B.J. Upton manufactured one run with his speed and later hit a two-run double.
The AL champions have dropped three straight following a season-best six-game winning streak. They fell to 14-22 on the road overall.
"We're just playing good enough to lose right now. We're just not getting the play, the hit or the catch," manager Joe Maddon said. "We're playing pretty well, actually, but it's tough to play from behind."
The injury-riddled Mets are 19-11 at pitcher-friendly Citi Field, with 13 wins in their last 18 home games.
Claimed off waivers in March and called up from the minors June 5, Nieve (2-0) has provided a much-needed boost for a depleted rotation that's also missing Oliver Perez.
"Here I feel more confident in all my pitches," Nieve said. "I want to show them that I can be in the rotation."
The 26-year-old right-hander made his first start for the Mets in a 6-2 victory at Yankee Stadium last Saturday, his first major league win in nearly three years.
He was just as good in this one, allowing one run and three hits in six innings.
"There's no doubt he's got good stuff," Schneider said. "He mixed everything in. His fastball jumps up to 95, 96 [mph] sometimes and I don't think a lot of people expect that."
His teammates have enjoyed playing behind Nieve, too.
"Two starts in a row he's just thrown gems," right fielder Ryan Church said. "He just gets the ball and goes. You know what you're going to get. He doesn't seem to get rattled."
Rodriguez, who squandered a one-run lead in Thursday night's 5-4 loss at Baltimore, earned his 18th save in 20 chances.
"I felt a lot better today," he said. "Everything was working. I was throwing the ball where I wanted to. My command was perfect."
Schneider's shot off Andy Sonnanstine (5-7) in the second inning was his first homer since connecting twice on Sept. 18 at Washington, his former team. The drive to right-center followed Gary Sheffield's single and a walk to Church.
"It was tough. Maybe I didn't give enough credit to Schneider," Sonnanstine said. "It was supposed to be an outside fastball and it kind of creeped back in. It's very frustrating."
Alex Cora singled to start the third and scored on Wright's two-out double off the right-field fence. Streaky all season, Wright snapped an 0-for-10 slide that came on the heels of a 24-for-43 surge.
Tampa Bay trimmed it to 4-1 in the sixth. Upton reached on an infield single, stole second and advanced to third on a wild pitch before scoring on Carlos Pena's RBI grounder.
Sonnanstine gave up seven hits in six innings, falling to 1-7 with an 8.22 ERA in nine starts on the road.
"It was one bad pitch, really," he said. "I felt confident and comfortable out there, but I do have to take ownership of this one as a loss."
LHP Johan Santana, coming off the worst start of his career, faces Tampa Bay RHP James Shields on Saturday. ... Church also stole two bases for the first time in his career, giving him five this season. ... The Mets are offering deep discounts on certain tickets for this series and the upcoming one against St. Louis.