VIDEO: Van Graan backs ref on red card
Munster, who held a 17-0 lead at half-time, lost the plot after the break – allowing Irish rivals Ulster to come back and clinch a bonus-point (24-17) win in their Pro14 Round 12 encounter on Monday.
Munster had two men carded in the game – replacement Fineen Wycherley was yellow-carded in the 54th minute and centre Sam Arnold red-carded four minutes later.
"I'm very disappointed after that start," van Graan said in his post-match reaction.
"In this game, you have got to keep 15 guys on the field and we went down to 13 and momentum went their way and left us in a very difficult spot.
"Sammy [Arnold] went for the tackle, hit him in the head and unfortunately the referee doesn't have any other choice than to red card him.
"I don't think it was intentional at all. I thought the spirit of the game was fantastic between two teams that were desperate to win.
Ulster coach Les Kiss also agreed the sending-off was deserved.
"You don't like to see anyone going off, but the referee had no option," said Kiss.
Munster also departed with a slew of injuries to Billy Holland (failed HIA), James Cronin (calf), Niall Scannell (shoulder/rib), Tommy O'Donnell (shoulder) and Calvin Nash (hip) as they prepare to host Connacht this Saturday.
Ulster will travel to Connacht.
