"I kept it up under control, kept the ball down, [I] felt pretty good about it," Niemann said.
He also said he doesn't get caught up in the pressures of bases-loaded situations, instead focusing on delivering the right pitch to get the Rays off the field.
Rays manager Joe Maddon commended the young righty on his much-improved angle and sharp breaking ball.
"I like what he did today because we've been talking specifically about keeping the ball down," Maddon said.
"Even the one A-Rod hit over the center fielder's head, that ball was down low."
Despite Yankees pitcher Heath Phillips' ejection on Wednesday for several threatening inside pitches, including one that hit Evan Longoria, Niemann said it was a non-factor for him.
"We definitely weren't not going to throw the ball inside because of all this stuff," he said.
Niemann said the early focus was on hitting the outside corner, and he pointed out that he threw inside frequently as the game progressed.
As for his first pitch, outside, to Shelley Duncan, who played a major role in Wednesday's melee, Niemann was equally dismissive.
"I'm not focused on who's in the box," he said. "I still have a job to go out there and do. I'm more concerned about that."
His focus paid off, as Niemann had superb control on the mound, rarely getting behind the 16 batters he faced, and finishing the day with no walks and a strikeout. The lone strikeout was a big one, sending Yankees captain Derek Jeter back to the bench.
"Things are going pretty well," said Niemann, who is still in contention to make the team's Opening Day roster.
"Things are getting better each time out, and hopefully will continue getting better," he said.