Nick Castellanos concerned Philadelphia Phillies fans when he exited Wednesday's game against the San Francisco Giants. The initial reason for being pulled from the game was not known. However, after leaving the field in the sixth inning, he was replaced by Edmundo Sosa. It was revealed by Phillies beat writer Matt Gelb that Rob Thompson pulled Castellanos out of the game because of left hip flexor tightness.

The Phillies are off to a good start this season, and Thompson is exercising caution with his star outfielder. Castellanos is one of Philadelphia's offensive leaders and a key part of the lineup. Before he left Thursday's game against the Giants, he chipped in an RBI and scored a run.

At 10-8, the Phillies are in a good spot in the early part of the NL East race. They are near the top of the division, although the New York Mets will fight them for the pennant throughout the season. Because of that, Castellanos was pulled and replaced by Sosa to prevent further injury.

The Phillies' outfield is already missing one of their regular starters. Brandon Marsh is considered day-to-day after hurting his right knee in Wednesday's matchup with the Giants. While it isn't serious, Phillies fans worry that the injury bug could follow the team throughout the regular season.

If Castellanos were to miss significant time for the Phillies, they would miss his bat in the lineup. He normally slides into the fifth spot in the Phillies' lineup behind sluggers Kyle Schwarber and Bryce Harper. His high batting average and power are a key part of one of the MLB's best offenses.

A healthy Philadelphia team is a scary proposition for the rest of the league. When whole, the Phillies roster has a plethora of All-Star caliber players, both in the box and on the mound.

The Phillies want to stay as healthy as possible in order to avenge their NLDS loss to the New York Mets. Nick Castellanos will be a deciding factor in whether or not the team achieves their goals.