Niemann became the first Tampa Bay pitcher to complete four innings this spring, leading the Rays to an 8-3 victory against the Orioles.
Niemann threw just 36 pitches while allowing one run and two hits. He was supposed to throw 50 pitches, so he headed to the bullpen for more work when his outing was over.
The Orioles have lost six straight. They committed five errors -- two by catcher Chad Moeller in the third and two more by rookie third baseman Josh Bell.
President of baseball operations Andy MacPhail, who's looking for improved fundamentals, was displeased by the team's performance.
"I don't like to lose games in spring training," MacPhail said. "More importantly than that, we have to play better defense than that. That probably concerns me more than the won-lost record. That's got to tighten up."
Baltimore didn't put up much of a fight against Niemann, who led the Rays and all AL rookies with 13 wins last year. Niemann had to fight to earn a spot in Tampa Bay's rotation last spring but this year he can just prepare for the season.
"It gives you a chance to get out there and work on things, allows you to relax and not stress, and honestly to get a lot more out of it," Niemann said. "In years past, when the high stress level is there, you can't really develop in spring."
In his two spring appearances, both against Baltimore, Niemann has allowed two runs and three hits in six innings.
"I do see a more relaxed player," Tampa Bay manager Joe Maddon said.
Asked whether he was upset with his team's approach, Orioles manager Dave Trembley said the focus is on preparing for the season.
"They should take their at-bats here in spring training and do what they think is best to get them ready for the season," Trembley said. "You know (Niemann's) going to throw it across the plate."
Evan Longoria had two RBIs for Tampa Bay. He doubled in a run in the first and hit a sacrifice fly in the third.
Chris Tillman pitched 2 1/3 innings for Baltimore, yielding two runs, one earned, and four hits.
Moeller homered in the third.
Orioles 2B Brian Roberts has yet to play this spring due to a back injury and Trembley said the leadoff hitter has been feeling ill. Trembley said Roberts would not be able to resume baseball activities until at least Thursday. MacPhail and Trembley think there's still time for him to be ready for the season opener, but MacPhail expressed some concern after the game. "The clock is starting to be an issue. It's getting to be on my radar screen," MacPhail said. ... Baltimore renewed the contract of All-Star OF Adam Jones for $465,000. Jones said he's open to signing a long-term deal with the Orioles. ... Baltimore signed 22 players and renewed the contracts of Jones, RHP Jason Berken, OF Nolan Reimold and C Matt Wieters. ... Maddon said he hopes to get 1B Hank Blalock into a game this weekend. Blalock reported to spring training after agreeing to a minor league deal. "He'll get some at-bats at DH," Maddon said. "I don't know how it fits yet. He's another guy that gives us at-bats -- depth-wise."