Steven Gerrard’s Rangers side were unable to stop Celtic from winning their 10th trophy in a row yesterday.
Frimpong was given his marching orders when he tugged back Rangers striker Alfredo Morelos in the box.
The full-back gave away a penalty just moments after Celtic had taken the lead in the contest through Christopher Jullien, and it looked like it was going to be a costly error.
However, Fraser Forster saved Rangers striker Morelos’s spot kick and Celtic held on to win the League Cup trophy.
Frimpong could not have been more relieved after the contest, but he admits he was full of nerves watching his teammates.
“Oh my days,” Frimpong said. “When you get sent off like that, I was inside panicking.
“It was the worst feeling ever.
“Every time Rangers got the ball I was just panicking.
“The time was going so slow but the team held it through and I am buzzing obviously.”
Celtic were on the back foot for much of the game against Rangers, but they were ruthless when their moment came.
Rangers were guilty of missing multiple opportunities throughout the game, and Jullien made them pay when he volleyed home a free kick.
Celtic have now won the last 10 trophies on offer in Scottish football, with Rangers struggling to stop their dominance.