The big righty threw 2 2/3 innings and allowed an unearned run on three hits and a walk to go with three strikeouts for Class A Advanced Port Charlotte.
"It was great to get back out there on the field and be in the game again and compete," Niemann said.
Niemann admitted nerves built up before he took the field, but once the game started, he calmed down.
The 29-year-old threw 41 pitches, four short of his allotted 45 by the Tampa Bay training staff. He didn't have to cover first base at any point and said his leg felt good.
Niemann's next scheduled start for Port Charlotte will be either Monday or Tuesday. He said he will be on a 60-pitch limit.
He added he still plans to return in late August.
"That's what we're hoping for, to follow the program and stay with it," Niemann said.
When Niemann got hurt, the Rays called up Alex Cobb from Triple-A Durham, and the righty has pitched well as of late, including a seven-inning outing Wednesday in which he gave up just one run on five hits.
"He's really stepped it up," Niemann said of Cobb. "It's been great to see, and everyone's been doing an amazing job out there. I can't wait to get back out there and contribute."