You were at the game obviously so didn’t have the advantage of seen by replays but their goal was caused by Bamba rather than Manga.
He got pulled into a ridiculous position by Steve Morrison, almost on the touch line, up by the half way line, so Sean Morrison had to leave Gregory and run across to cover leaving both centre half’s well out of position.
Gregory exploited this and made a great run to be fair (I thought his off the ball running and movement was excellent all night) and so very harsh to blame Manga IMO