Red Sox place 3B Kevin Youkilis on 15-day DL (Yahoo! Sports)
BOSTON (AP) The Red Sox placed third baseman Kevin Youkilis on the 15-day disabled list Wednesday because of a strained back.
Boston also promoted Triple-A prospect Will Middlebrooks to take Youkilis' roster spot.
Youkilis had been a late scratch the past three days, and manager Bobby Valentine said he has improved but wouldn't have been able to play for at least another four days. He last played Saturday night in a 1-0 win over the Chicago White Sox.
Youkilis has struggled this season, hitting just .219 with two homers and nine RBIs in 18 games. He feels that his back was getting better, but knew he needed to go on the DL.
''Things are going well but they want to get a step ahead of it and get me as healthy as possible,'' he said before Wednesday night's game against Oakland.
Middlebrooks was hitting .333 with nine homers and 27 RBIs in 24 games with Pawtucket. He was inserted in the starting lineup, batting eighth and playing third.
Valentine also said Josh Beckett would miss his next start Saturday because of soreness in his right side and Aaron Cook would be placed on the roster and pitch in his place. Cook, who had an opt-out clause if the team did not recall him soon, went 3-0 with a 1.89 ERA in five games with Pawtucket.
''Aaron Cook's been retained by us,'' Valentine said. ''We're going to keep him, start him Saturday in Josh's spot for one start.''
Valentine said Beckett's high pitch totals his last two starts has the right-hander dealing with more soreness than usual.
''We're going to play it safe,'' he said. ''He's been throwing more pitches and he has some lat stiffness.''
Boston also recalled right-hander Clayton Mortensen from Pawtucket to fill a roster spot after Lars Anderson was optioned back after last night's 5-3 loss to the Athletics.
Mortensen, acquired in a trade for shortstop Marco Scutaro during the offseason, allowed two runs in six relief appearances with Pawtucket.