Wales number eight Taulupe Faletau suffered another injury blow on his Cardiff comeback after a six-month injury lay-off.

He returned for Cardiff's defeat by Ulster in the United Rugby Championship but was forced off in the 30th minute.

Faletau, 33, was clutching the same arm he damaged in France.

Cardiff head coach Matt Sherratt is hoping it is not the same injury.

"He is being assessed after having a knock on his shoulder and we don't know the extent of the injury yet," said Sherratt.

"It is not the same injury from my understanding.

"Fingers crossed, it's not too bad because he's put a huge amount of effort in over the last six or seven months to come back.

"I am gutted for Toby. I'm sure the boys will get around him."

Cardiff's Wales full-back Cameron Winnett was also forced off early on in the game.

Wrong side of calls

Cardiff suffered an agonising 19-17 defeat in which they found themselves on the wrong end of decisions by Scottish referee Mike Adamson.

Cardiff were unhappy about a knock-on not being picked up in the build-up to Ulster''s try by Dave McCann with Adamson saying there was no good angle from the television match official (TMO).

"I have not criticised the referees all season and whatever call they make is just what they have seen in the game," said Sherratt.

"What we have struggled with tonight was there was a clear knock-on in the build-up to their try from the line-out. There is no doubt about it.

"I can see the referee is unsighted, but you have a touch judge seven metres away looking straight at it and that is seven points."

After Cardiff flanker Thomas Young was denied a try when the ball was kicked out of his hands by Ulster replacement Cormac Izuchukwu, the visitors thought they had secured the win only to see what would have been Theo Cabango's hat-trick score ruled out.

Play was brought back for an Ulster penalty for a deliberate knock-on from replacement prop Rhys Carre with John Cooney kicking a 79th-minute winning penalty.

"I will have to have a better look at it because I only saw it on the screen, but I am not sure whether that is a clear enough or obvious penalty at the end to overrule a try and give a penalty under the sticks," said Sherratt.

"I might be wrong on that, but my instinct is it has to be clear and obvious to overrule something like that and it did not seem that to me."

It was a 10th defeat in 14 league games this season for Cardiff with nine of those yielding losing bonus points for finishing within seven points of their opponents.

"We deserved more from the game," said Sherratt.

"It is difficult at the end of the game because it is emotional and you don't want to say anything out of emotion.

"When the dust settles, we need to look at things we can do better. We need to be able to put more pressure on the opposition and score more points.

"We are putting ourselves in a position where it is always coming down to a referee call or a last minute penalty, as it did tonight."