Penrith Panthers forward Spencer Leniu will miss a number of weeks as he recovered from a ruptured testicle.

The painful injury was sustained by the prop at training earlier this week, with the Panthers forced into a late change for Friday night's game against the Sydney Roosters.

The Panthers, in a short statement, labelled the injury a 'high impact' one.

"Panthers prop Spencer Leniu has been ruled out after suffering a high impact injury at an opposed training session on Wednesday night," the club wrote.

"The incident resulted in Leniu suffering a ruptured testicle, which required him to undergo surgery at Nepean Hospital.

"The representative prop is recovering well at home, with a return-to-play date yet to be determined.

The injury will end any chance of Leniu being a surprise bolter for Brad Fittler's New South Wales Blues State of Origin squad, with the opener on May 31, and the squad to be named on May 21 - following the completion of Round 12.

More immediately, it means Leniu misses a game against the team he will play for next year in the Roosters, with Liam Henry coming onto the bench in his absence, while Liam Martin is still in the 19-man squad and a chance of playing when it kicks off at 8pm (AEST) this evening.

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According to The NRL Physio, the injury is likely so sideline Leniu for at least two weeks, but as potentially as many as six.

That means, in the best case, he will miss Round 11 and 12 against the Roosters and Broncos respectively, before being a candidate to return in Round 14 against the Dragons after a bye.

In the worst case, he would also miss a second clash against the Roosters in Round 15, a game against the Cowboys in Round 16, and would likely be back on the park for Round 17 against the Knights.