Sampson has pitched in two games this spring but Sunday will be his first start. He's been doubling up with other rotation candidates and entering games as the second starter.
"It'll be nice to work on a pregame routine starting as well," Sampson said. "I'm just excited this neck thing went away and I'm ready to go."
Sampson was slated to pitch against the Reds in Sarasota, Fla., on Tuesday, but he woke up that morning unable to turn his neck to one side after sleeping on it wrong.
The right-hander is one of nine pitchers in the mix for a starting job. He was seemingly pushed aside when Shawn Chacon signed a one-year deal shortly after pitchers and catchers reported to Spring Training, but Sampson, who can start and relieve, is still in the running.
Also recovering is catcher J.R. Towles, who was cleared to do some light jogging on Thursday to test his strained hamstring.
"He's making progress," manager Cecil Cooper said. "If things go the way we hope, [he'll play] the early part of next [week] or hopefully by the middle, anyway."
Closer Jose Valverde threw in the bullpen on Wednesday but will not appear in a game for at least another day. The right-hander has been nursing a sore back.
Second baseman Kazuo Matsui, who hasn't played in a spring game in nearly a week, said on Thursday, "I'll try and be ready for the weekend."
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.