Reading manager Brian McDermott promised his club would do everything they can to track down the fan responsible for throwing a coin that struck West Brom's Chris Brunt.
After the FA Cup fifth-round tie at the Madejski Stadium – which West Brom lost 3-1 – Brunt went over to the visiting fans, but was struck underneath his left eye by a coin thrown from the crowd.
The Northern Ireland international said he was "disgusted and ashamed" by the incident, while McDermott was similarly scathing in his reaction.
"That's outrageous really, it's not right and proper," he said. "We will cooperate, I am sure, and make sure we find the person who threw it."
The unsavoury incident took some of the attention away from an impressive victory for Reading, who fell behind to Darren Fletcher's effort before goals from Paul McShane, Michael Hector and Lucas Piazon sealed a shock win and a place in the quarter-finals.
"There's a great camaraderie between the players and staff and there was a fantastic atmosphere here, so it gives the boys confidence going in against Rotherham [in the Championship on Tuesday]," McDermott said.
"Considering who you're playing against, a Premier League side, who know what they're doing and they know how to win games. They've won at Everton last week.
"Tony [Pulis] has put out a strong side, so it's a great result for us and we'll look forward to the draw.
"To get a couple from set-plays is fabulous, especially against that team. I know that Tony would pride himself on not conceding from set-plays."
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