Pittsburgh Steelers linebacker TJ Watt underwent surgery on Thursday to repair a partially collapsed lung after falling ill at team practice this week.

Watt was rushed to hospital with the troubling health issue on Wednesday, before having the procedure the following day, according to ESPN's Adam Schefter.

It is believed the 31-year-old will be discharged from hospital on Friday, yet he still won't be fit in time to face the Miami Dolphins on Monday night after being ruled out by Pittsburgh.

The Steelers confirmed his medical scare in a statement on Thursday while revealing he would not take further part in practice and his status for Week 15 was in question.

The team said: 'T.J. Watt is currently in a local hospital for further medical evaluation of his lung after experiencing discomfort at the practice facility on Wednesday.

'He will not be at practice on Thursday, and his status for Monday night's game vs. Miami is in question. Coach [Mike] Tomlin will provide more updates at the appropriate time'.

Schefter later reported that Watt's injury occurred during treatment at the team facility before he was taken to hospital.

Back in the summer, Watt signed a three-year, $123million deal with the Steelers - making him the NFL's highest-paid defender in the process.

The four-time All-Pro's contract also includes $108m guaranteed, while he is set to earn $21m this season in the final year of his previous deal.

Watt's issue comes just days after his Steelers teammate, receiver DK Metcalf, was hospitalized after experiencing stomach pains on a journey back to Pittsburgh.

Metcalf boarded a flight home with the rest of the Steelers team after their win over the Baltimore Ravens, only to begin suffering from stomach issues.

Pittsburgh medical staff removed the 27-year-old from the plane and sent him to a hospital in Baltimore 'out of an abundance of caution.'

After being evaluated, he later spent the night in a hotel and is set to fly back to Pittsburgh on Monday.

Metcalf was on the wrong end of a hard hit during the win at M&T Bank Stadium and medical staff sent him for tests in a bid to rule out serious internal injuries, NFL Network reported.