PHILADELPHIA -- The Phillies' bullpen threw a combined 24 innings the previous four nights.

They needed another fresh arm.

They got one before Sunday's series finale against the Red Sox at Citizens Bank Park. They optioned left-hander Sergio Escalona to Triple-A Lehigh Valley and selected right-hander Tyler Walker's contract from Lehigh Valley to take his place.

Escalona joined the Phillies on Saturday -- he replaced right-hander Kyle Kendrick, who had been called up Friday -- but after left-hander Antonio Bastardo lasted just one inning Saturday, they needed Walker.

The Phils' bullpen has thrown 209 2/3 innings this season, which ranks sixth in the Majors.

"Based on the way the bullpen has been used the past few days, I figured something might shake out," Walker said.

Walker went 2-1 with a 1.42 ERA and three saves in 15 appearances for the Iron Pigs. In six seasons in the Majors, he is 20-17 with a 4.52 ERA and 34 saves. He went 5-8 with a 4.56 ERA in 65 appearances last season with the Giants.

The Mariners released Walker at the end of Spring Training. He signed a Minor League contract with the Phillies on April 9.