"I went in there and wanted to throw strikes and keep the ball down and let the defense do the work, and they played great behind me today," said Peacock, who threw 71 pitches. "That's what I wanted to do."
The pitcher who doesn't make the rotation will pitch out of the bullpen.
Peacock, acquired in early February from Oakland in the Jed Lowrie trade, pitched 19 2/3 innings this spring and allowed 16 hits and seven earned runs. White, acquired in December from the Rockies, allowed 33 hits and 15 earned runs in 19 2/3 innings.
"The good news is we have until Saturday to make a decision, because that fourth starter doesn't go until [April 5 against Oakland]," Porter said. "It's something that we'll sit down and talk about and make a decision."
The rest of the rotation is set with Bud Norris, Lucas Harrell, Philip Humber and Erik Bedard, who's been appointed the fifth starter.
Peacock had good fastball command at George M. Steinbrenner Field and wished for better secondary stuff, though Porter was happy he threw a pair of sliders to left-handers. For Peacock, who had a rough 2012 at Triple-A Sacramento, it's about confidence.
"In the dugout, I visualize what's going to happen, what hitters are coming up," he said. "I just want to throw that pitch, what I see in my head. That's what I do."
Peacock and White have developed a close relationship over the past few weeks and are cut from the same cloth -- soft-spoken Southerners who just want to help the Astros win.
"I don't care where I'm at," Peacock said. "I'm real excited I made the team, and hopefully I can take advantage of the opportunity."
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.