Chelsea players had to force a straight face to avoid being caught laughing at the touchline clashes between Antonio Conte and Jose Mourinho, substitute goalkeeper Asmir Begovic admitted.
The managers confronted each other during a heated FA Cup quarter-final at Stamford Bridge, with Manchester United's Ander Herrera given two yellow cards for fouls on Eden Hazard in the first half before N'Golo Kante fired Chelsea to a 1-0 win.
Conte accused United of targeting Hazard throughout in his tactics and expressed his anger with his Portuguese counterpart in a heated exchange.
Although Begovic felt the tension was unnecessary, he admits the antics made it tough for those watching to keep themselves from laughing.
"It was a huge opportunity, a great match at the Bridge. As much as I was disappointed that I wasn't playing, I was in the front row to see the amusing antics along on the touchline," said Begovic.
"The coaches clashed, they shouted at each other, it was a very intense match. It was really unnecessary, but it was so funny, because I worked so hard not to laugh. Every time the camera came across, we thought to ourselves 'be serious, don't get caught laughing'.
"It was unprofessional, and I thought it was a little too much. They had a fight, it was a big deal and I don't think we like to see that."
The two sides meet again at Old Trafford on 16 April in the Premier League, a week before Chelsea face Tottenham in their FA Cup semi-final tie.