Youkilis will start as the designated hitter for the PawSox, who begin a four-game series with the Durham Bulls on Tuesday night.
"We're going to try to get him three at-bats tomorrow," said manager Bobby Valentine. "He'll start tomorrow and we'll get him enough [playing time], whatever it's going to take to have him say that he feels good."
The third baseman, who hasn't played since April 28, took batting practice and fielded ground balls for the third straight day on Tuesday before Boston's series finale with Seattle.
Youkilis is likely to play at least two games in the Minors before returning to the Red Sox.
"He looked really good taking his ground balls today, moving around, bounce in his step," Valentine said. "He'll probably go from DH to playing in the field, seeing some pitches."
Youkilis won't be the only player on a rehab assignment for Pawtucket's series with Durham. Starter Daisuke Matsuzaka, who had Tommy John surgery last year, is scheduled to make his fifth rehab start for the PawSox on Thursday.
Youkilis' rehab assignment means rookie Will Middlebrooks will remain in the lineup for now. Middlebrooks started at third base Tuesday for the 12th time since being recalled from Pawtucket on May 2.
Middlebrooks entered Tuesday's game with nine extra-base hits (four homers, five doubles) and 13 RBIs in 11 games, tied with Mo Vaughn for the most by a Red Sox player in his first 11 games since 1918. Vaughn accomplished the feat in 1991.