The Phillies and Velasquez indicated Wednesday, however, they do not believe the injury is serious. Manager Pete Mackanin said Friday that Velasquez's MRI came back "pretty clean," and the pitches reiterated his lack of concern.
"It's just a little strain, just a little fluid in there," Velasquez said, citing the results of the MRI. "We'll shoot for 15 days and go from there. I don't know how many days. It might take 10, five, who knows."
Velasquez had a 2.42 ERA through his first eight starts this season. But in his previous three outings before the injury, he posted an 8.31 ERA while not making it through five innings in any of those games.
Velasquez first felt something while warming up in the bullpen Wednesday, but the injury could have accounted for his recent struggles.
Velasquez was the key piece in the Ken Giles trade with Houston in December. The Phillies originally agreed to send Giles to the Astros for a four-player package that included right-handers Velasquez and Thomas Eshelman, left-hander Brett Oberholtzer and outfielder Derek Fisher.
However, the Phillies had apprehensions about Velasquez's physical. He had Tommy John surgery in 2010, but sources also said the club had concerns about his shoulder.
In the end, the trade got delayed a few days and was reworked. The Phillies sent Giles and Minor League infielder Jonathan Arauz to the Astros for five pitchers: Velasquez, Eshelman, Oberholtzer, Mark Appel and Harold Arauz.
Velasquez does not believe the biceps strain could lead to something like another elbow surgery.
"It's just more in the biceps area," he said. "It's just something that's probably more minor. This is not something to be too worried about."
Eflin will make his Major League debut in place of Velasquez on Tuesday. The Phillies acquired the righty from the Dodgers in exchange for Jimmy Rollins in December 2014. The 22-year-old entered the season as Philadelphia's 13th-ranked prospect according to MLBPipeline.com. He has a 2.90 ERA in 68 1/3 innings this season at Triple-A Lehigh Valley.
Until Eflin arrives, Garcia will join Philadelphia's bullpen. The 29-year-old righty has a 3.90 ERA in 113 career innings and has thrown one scoreless inning at the Major League level in 2016.
"He's got stuff to be a real good pitcher at this level," Mackanin said of Garcia. "It's always about command, control. If you can command your stuff, throw quality strikes, he's got the ability to be a real good relief pitcher."
First baseman Ryan Howard is batting only .150 on the season, with a .559 OPS, prompting a gradual decline in his playing time as Tommy Joseph continues to hit well. Howard has only 10 at-bats in June and was not in Philadelphia's lineup Friday against the Nationals. Mackanin said before the game he would talk to Howard, "just to let him know what his status is."