WASHINGTON -- Ryan Howard's ailing left knee kept him out of the lineup for Sunday's series finale against the Nationals, and manager Charlie Manuel said after the game that he was not sure if Howard would start on Monday in Boston.

"There's a chance he'll play," said Manuel, who could use Howard at designated hitter in the American League park. "We'll see."

A week ago, Howard received a cortisone injection in the knee, then had an MRI exam that revealed inflammation and some cartilage tears. He has continued to play, but Manuel said the knee had been sore for the past couple of days. That, and not Howard's four-strikeout performance on Saturday, was the reason he wasn't in Sunday's lineup.

Howard did appear as a pinch-hitter in the eighth inning, bouncing into a 4-6-3 double play.

With Howard out, Kevin Frandsen started at first base, and Michael Young stayed at third. Right fielder Delmon Young, who was 5-for-15 with two home runs over his previous four games, got his first start of the year in the cleanup spot but went 0-for-4.