He'd landed awkwardly following a foul by Villa's Fabian Delph, received treatment but collapsed in a heap immediately he returned to the pitch.
The noises coming out of Turf Moor on Monday were that it was nothing too serious. He didn't attend the club's end of season awards night but the news was that he was just resting up and that he'd be back soon.
So it seemed, with another 11 weeks to the next competitive game, that we had little to worry about and that he'd be fit and ready for pre-season, but that was dashed yesterday with early speculation that the injury was more serious.
Although not confirmed by the club as yet, the news coming out from our local press that he's suffered a ruptured anterior cruciate ligament injury is correct and my understanding is that he might also have suffered damage to his medial ligament.
That, I expect, will rule Barnes out for much, if not whole, of next season and that's a massive blow both to him and to the club.
He had to wait for his chance this season and started just one of the first ten games when we were searching for our first win. That one start came in the 2-2 draw at Leicester while he added seven substitute appearances to that, missing out totally only when he was an unused sub for the 0-0 home draw against Sunderland and not even making the match day squad at Arsenal.
Since, he's started every game other than the home defeat against Leicester when he was suspended. He's only scored five goals during the season but has turned in some outstanding performances, none more so than the away draws at Manchester City and Chelsea.
He's formed a very good partnership with Danny Ings but we are now facing a season without the pair of them with Ings set to move on some time during the summer.
To have a player suffer such an injury is one thing, but for a club to see it happen to four of its players in a 14 month period is devastating news.
Sam Vokes, the first of them, is now back to fitness and playing again, but Barnes, who I believe will be operated on in the next week, will join Kevin Long and Dean Marney in rehabilitation.
A new striker was always going to be on the shopping list for the summer but this news could see us having to bring in two in readiness for the big kick off in August.