Connacht have suffered yet another season-ending injury with talented 22-year-old Eoghan Masterson ruled out of action.

The back row player suffered a serious knee injury in the 45th minute playing against Zebre in Parma at the weekend, and although the extent of the injury is still unclear, coach Pat Lam says he will “definitely” be out for the rest of the season.

After an x-ray in Parma, Masterson travelled home with the team on Sunday evening before undergoing further scans yesterday.

“You could see at the time it was serious. He’s had a very good season, and is a big loss. There is a good fight in the back row, we have had guys in and out, and Eoghan can play eight, seven or six. But the most important thing is that every time you have an injury, you lose the competition, and that is what is driving everybody.”

Sean O’Brien, having returned from concussion, James Connolly, having played for Corinthians in their Ulster Bank League win last weekend, both come back into contention.

However three key players will be monitored ahead of the Ospreys’ visit on Saturday - openside Jake Heenan suffered a hip pointer, centre Craig Ronaldson a knee ligament, and Eoin McKeon a grade one ankle injury. Centre Rory Parata is also ruled out for the next two weeks with a knee cap injury in training, and is awaiting a report to determine if surgery will be required.

Connacht currently sit on the top of table with 50 points, but Lam says Connacht will still need to ramp it up this weekend against an Ospreys’ side 12 points behind in seventh place. Despite scoring 51 points in Italy, Connacht conceded 34 to the Italian side on the back of mistakes.

“You are going to lose the ball at some stage. Zebre came out fired up and when they got the ball, they ran it back, so it was a good learning and it has altered our training for the next part of the season.

“There is a lot of belief in the way we play, a lot of confidence, and a lot of rough edges, It is a step-up against the Ospreys, so it is a massive game this week.”