Aberdeen manager Craig Brown absolved Keith Lasley of blame after the Motherwell midfielder was sent off for a challenge on Fraser Fyvie.
Lasley was sent off for a slide tackle on the 18-year-old during Aberdeen's 2-1 Scottish Cup win at Fir Park and Fyvie was stretchered off.
"Keith didn't mean that," Brown told BBC Radio Scotland's Sportsound.
"No way was that a deliberate attempt to injury a player."
Aberdeen impressed at Fir Park, racing into a two-goal lead thanks to a double by Rory Fallon.
Dons goalkeeper Jason Brown then saved a Michael Higdon penalty before Nicky Law's goal set up a grandstand finish.
Lasley's tackle led to Fyvie being stretchered off, but the Aberdeen boss refused to point the finger at the Motherwell midfielder.
"Young Fyvie has a very sore ankle. It looked naughty, but I'm not complaining; I never complain about decisions that go against us," he said.
"In actual fact, that decision went against us because it gave Motherwell the persecution complex: down to 10 men with nothing to lose.
"Lasley is the last man, in my book, to be a dirty player."
Brown felt his side struggled to make their numerical advantage pay dividends.
"We did not play well against 10 and I have to give credit to Motherwell because they were exceptionally positive with a man short," he said.
The 2-1 win at Motherwell set up a last-four clash with Hibernian on 14 April at Hampden.