Limping in the first-half, he lasted 57 minutes before succumbing to the inevitable.

He said: "How do I view that? Probably the clientele we were coming up against was one thing and the importance of the game.

"If I didn't think I would have added to the game I would have pulled it myself. It was one of those things where I had to get through it."

O’Brien has since sat out the Guinness PRO14 wins over Munster and Connacht. He will be a spectator again when Ulster visit the RDS this Saturday but he expressed a confidence on Wednesday afternoon about his hopes of featuring in Europe next week against Glasgow.

He describes the issue as akin to having a tight muscle and one that was causing him to labour as he ran through the gears from a jog to three-quarter pace. But there were no fears of an aggravation that would have put his Six Nations ambitions into doubt.

He said: "It's not a bang, though. It's not like I was after getting a knock. It was just tightness and there was nothing really that I could have pulled or anything like that. It just would have got sore. So that's why I played, but I felt good to play."

O’Brien had both hips operated on back in 2012.

"It's probably from childhood because I've got shallow hips,” he said. There had been no further issues with either until now, although he has had plenty of other injuries to contend with before and since.

The two-time British and Irish Lion tourist has spoken before about his impatience in returning too soon from one injury or another but he accepts that there comes a time when caution should win out over valour.

“You can hide stuff from physios and management and get through stuff without showing it but you know in the bigger picture then that you could break something down the line. So, it's just getting it right now.”

Meanwhile, Joey Carbery is still hopeful of making a first ever Six Nations appearance. The versatile back fractured his left wrist in November but has had the cast removed and his back on the pitch training.

"Yeah, hopefully anyway,” he said at a Lifestyle fans’ competition. “Even maybe the last European game (away to Montpellier on January 20) but I’m not too sure because you never know how tomorrow goes. So, fingers crossed anyway.”

No injury is welcome but Carbery’s struck at precisely the wrong time given Leinster senior coach Stuart Lancaster had already spoken about him being afforded some badly needed game time at ten with the province over the holiday period.

“Yeah, definitely. It was annoying because I was just getting a bit of time at ten, even with Ireland, and it would have been good to get a few games under my belt. Now I just have to work hard and hopefully get back in the team.”