Pittsburgh Steelers tight end Pat Freiermuth is set to sit out the team's upcoming game against the Los Angeles Rams on Sunday after re-aggravating his hamstring injury, according to reports from NFL Network's Tom Pelissero. The setback is anticipated to keep Freiermuth out for an extended period of time.

Freiermuth underwent an MRI on Friday morning to assess the severity of the injury. The 23-year-old initially suffered the hamstring injury during the team's Week Four loss against the Houston Texans. As a result, he missed the subsequent game against the Baltimore Ravens but had been expected to return following the Steelers' Week Six bye.

However, the young tight end's participation in practice this week took a turn for the worse. After a full practice session on Wednesday, Freiermuth was limited on Thursday, raising concerns that he had aggravated the hamstring injury once again. The setback has thrown his timeline for return into uncertainty.

So far this season, Freiermuth has caught just eight passes, although two of those receptions resulted in touchdowns. With his absence from the lineup, rookie tight end Darnell Washington is likely to see an increased workload. The injury comes at a challenging time for Freiermuth, who had been aiming to make strides in his third season and build on his connection with quarterback Kenny Pickett.

Even before the injury, Freiermuth had been struggling to find his rhythm in the Steelers' offense, which has been one of the league's weakest in the early part of the season. His most productive outing came in Week Three against the Las Vegas Raiders, where he recorded three receptions for 41 yards and a touchdown. However, his involvement in the passing game has remained limited, and he has encountered difficulties as a blocker as well.

Through the first five games of the season, Freiermuth's performances have been underwhelming, grading out at 54.0 overall, including individual ratings of 56.4 as a receiver and 52.1 as a run blocker, according to Pro Football Focus. These marks are on pace to be career lows for the third-year tight end.

Week Seven was poised to provide a favorable opportunity for Freiermuth as the Los Angeles Rams have struggled to contain opposing tight ends. However, with his injury setback, the game will provide an opportunity for players like Darnell Washington and second-year tight end Connor Heyward to step up and contribute in the passing game.

The results of Freiermuth's MRI are awaited in the days to come. Nevertheless, it is highly likely that Freiermuth will be facing an extended absence from the Steelers' lineup due to the re-aggravated hamstring injury.