To replace him on the roster, the Phillies purchased the contract of righthander Michael Stutes, the 24-year-old who turned heads in spring training. He will join the team Monday in Phoenix.
Twenty-one games into the season, the Phillies are down two closers. With Brad Lidge already sidelined for at least another few months with a partially torn rotator cuff, Ryan Madson takes over as closer.
That leaves the eighth inning for Bastardo and, well, anyone's guess.
"It's thin," general manager Ruben Amaro Jr. said of his team's bullpen. "It is what it is."
Amaro said Contreras first felt the soreness after his outing Thursday. He threw 26 pitches for a save, and it was the fifth time he had thrown in seven days. In total, he threw 81 pitches during that span.
After being a starter for his whole career, Contreras was not a full-time reliever until last season. He signed a two-year, $5.5 million deal (with a 2013 club option) in the winter. The recent heavy workload caused this injury.
Charlie Manuel said after Saturday's game there was a "90 percent chance he'll definitely be ready" for Sunday. Amaro said the soreness was improved Saturday but then worsened Sunday.
"I think it was just the work that he's done," Amaro said. "He didn't indicate it was one pitch, just over time, especially after his outing on Thursday."
Contreras had not allowed a run in eight innings while converting all five save opportunities. He struck out nine and walked four.
Given few effective options in the back of his bullpen, Manuel has ridden Contreras and Madson hard early. Madson did not pitch Sunday for the second straight day but bluntly said it was rest for "normal" soreness.
"Nothing to be concerned about," Amaro said. "It's a long haul. We want to be careful with them. We don't want to use him too much, but at the same time we're trying to win baseball games."
There was a trickle-down effect when Lidge went down, and that led to Contreras' overuse and subsequent injury. It provides an opportunity for Stutes, who continued to pitch well after his effective spring. In 10 innings at triple A, Stutes allowed two runs and struck out 14 with four walks.
It also opens a door for Madson, a free agent at season's end, who now has the opportunity to close.
"We don't need labels," Madson said. "A couple years ago we were talking about nobody needed to know when they were pitching and nobody cared. We don't want labels now, anymore. Just go pitch. Get people out."
John Mayberry Jr. started in left field as Raul Ibanez, 0 for his last 18, sat. Mayberry was 1 for 4 with an RBI double. . . . The Phillies are 22-4 all-time at Petco Park. They have won their last 11 here. The four-game sweep in this city was the Phillies' first since 1979. . . . Shane Victorino's inside-the-park home run was the Phillies' first since July 9, 2009, when Chase Utley did it against Cincinnati in Citizens Bank Park.
Contact staff writer Matt Gelb at email@example.com. Follow him on Twitter at twitter.com/magelb