The Red Sox pitching staff may have just been dealt a serious blow.

James Paxton, who started Sunday’s series finale against the Houston Astros, left after suffering a right leg injury during the top of the first inning. Paxton had only thrown five pitches when he pulled up and went down to one knee, and after being checked by the trainers he struggled to put any weight on his injured leg as he was helped off the field.

As of this writing the Red Sox have not provided an update on the nature of Paxton’s injury or its severity.

Losing Paxton for any length of time would be a serious setback for the Red Sox rotation. The veteran left-hander was acquired from the Los Angeles Dodgers at the trade deadline to help fortify the club’s pitching staff, which had already suffered heavy losses after both Lucas Giolito and Garrett Whitlock were lost to season-ending injuries early on.

This is a breaking news story. Check back later for additional updates.