ADAM O’Brien brushed aside Adam Walker’s challenge on him as “part and parcel of rugby” as the Bulls crashed out of the Challenge Cup in controversial fashion.

Hull KR prop Walker floored O’Brien with his right hand shortly before half-time following a tackle and referee Matt Thomason opted to sin-bin him rather than show a straight red card.

Bulls forward Adam Sidlow was also sin-binned for his part in the melee – a decision which left boss Jimmy Lowes and the home fans furious.

Bulls hooker O’Brien said: “I just got up at the play-the-ball and felt a hand to the face.

“I had hurt my ankle in the previous play and that was hurting me more, so when I got whacked in the face I went down and was holding my ankle more than anything.

“It’s part and parcel of rugby and some players have a bit of an attitude.

“He has thought ‘I’ll give a little hooker one in the face’ and I think that’s all it was.

“I don’t think I’d made a dirty tackle – I just think he has retaliated and gone to lash out in my face.

“I tackled him and was getting up but then saw this arm come across and smack me in the face.

“I think it was a push or a palm in the face rather than a punch.

“You can’t lash out like that at the marker as it could be a red or a sin-binning.

“I think it was tough on Adam Sidlow. He has come to sort it out and he’s got sin-binned as well.”

The Bulls went toe-to-toe with Rovers for over an hour before Josh Mantellato’s three tries in quick succession in the final quarter eased the visitors home.

O’Brien added: “For the 70 minutes we were the better side in my eyes, but they got a few late tries and I think it deflated us a bit.”

Bulls boss Jimmy Lowes, who lost Chris Ulugia to injury at half-time, was proud of his players’ efforts.

On the incident which saw Walker and Sidlow sinbinned, Lowes said: “Potentially that might have been a turning point but I’m proud of the players, that’s never in doubt, because they work hard.

“Hull KR are a good side, very clinical, but we offered them fifty points worth of chances and they took them.”