The Philadelphia Phillies are in quite a precarious situation heading into the Aug. 3 trade deadline, as an injury to a key bullpen arm may force them to reevaluate their plans. 

According to ESPN's Jeff Passan on Thursday, Phillies reliever Brad Keller will miss the rest of the season after it was found he had torn his UCL ligament in his right arm. Keller is likely facing Tommy John surgery to repair the ligament, or the alternative internal brace procedure, which would mean he'll miss all of next season, too. 

Add in the potential of a work stoppage between Major League Baseball and the MLBPA; Keller's time as a Phillie may be over before it gets off the ground. Signed to a two-year ($22 million) contract this past offseason to be one of the Phillies' top right-handers in the bullpen, Keller's addition has proved to be a dud. In 32 appearances this season, the 30-year-old posted a 4.02 ERA in 31 1/3 innings. 

Keller had been on the injured list since June 14 with forearm tendinitis and was activated from the IL on July 8. Available to pitch in the Phillies' series against the Cincinnati Reds and Detroit Tigers, interim manager Don Mattingly said he wanted to "stay away" from using Keller when the Phillies took on the Tigers. 

The Phillies' need for a bullpen arm becomes more of a concern

Heading into the Aug. 3 trade deadline, the Phillies had three holes to fill: finding a starting pitcher, a right-handed bat with some pop and a backend bullpen arm. Now, the concern shifts to finding a bullpen arm as the most important move. 

With Keller down, the Phillies will need the likes of Jonathan Bowlan and Orion Kerkering to step forward and be the ones who hand the baton to Jhoan Duran. Bowlan has shown the ability to take down high-leverage situations, as he has not allowed an earned run in the seventh inning this season (five innings) and has a solid 3.09 ERA in the eighth inning (11 2/3 innings). 

Kerkering has also done well in the latter innings, posting a 1.54 ERA (11 2/3 innings) in the seventh inning and has struggled a little in the eighth inning (3.63 ERA in 17 1/3 innings). 

Outside of Bowlan and Kerkering, the Phillies have options down in the minor leagues to come up and eat innings. The most notable name would be right-hander Alex McFarlene. 

On the 40-man roster and dominating at Double-A Reading -- the 23-year-old has posted a 2.12 ERA and struck out 45 in 34.0 innings -- McFarlene would likely be the first to get a call-up. Touching 100mph with his fastball, McFarlene, coming up and having success, could help the Phillies not trade for two relievers at the deadline.