Chelsea head coach Antonio Conte feared Eden Hazard would be seriously injured during the bad-tempered 1-0 win over Manchester United at Stamford Bridge.
N'Golo Kante scored the only goal after Ander Herrera was sent off for two bookable offences for fouls on Hazard.
It seemed the Spain midfielder was carrying out an apparent edict from United boss Jose Mourinho to target the Belgium midfielder.
Conte called for Hazard to receive protection from officials. It is a call Mourinho has made previously, when he was Chelsea manager.
"For Hazard, (for) 20, 25 minutes it was impossible to play football, because he received only kicks," Conte said.
"A tactic to play and go to kick an opponent? It's not football for me.
"I don't think that I'm crazy and I see only him in this situation.
"Sometimes when you play against players with great talent, you try to intimidate those players.
"The referee must protect these type of players. When they go out with a bad injury...
"It's very dangerous to receive a kick from the back."
Conte did not see the incident which saw United defender Marcos Rojo apparently tread on Hazard's back as the Chelsea forward was falling to the turf. Rojo could face retrospective action from the Football Association.
Mourinho's comments on Herrera's dismissal by referee Michael Oliver were laced with sarcasm.
Mourinho told the BBC: "I think we all watched the match until the red card and after the red card and then we can compare the decision of the two yellow cards in this case with other ones that were not given, but I don't want to go in that direction.
"Mr Michael Oliver - a referee with fantastic potential. Manchester United were a bit unlucky. In four matches, three penalties and one red card in such an early moment of the game but again I cannot change that.
"Mr Oliver goes home and he can do his own analysis, because I don't want to analyse his work."
Pressed further in the post-match media conference, Mourinho suggested Gary Cahill should have been disciplined.
Mourinho said: "I don't want to speak. I just tell you to compare Herrera second yellow card, which is a yellow card in the bad zone and you compare that with a couple of minutes later when (Marcus) Rashford goes to attack the space and the Chelsea captain grabs him and stops him in a counter-attack situation.
"So Mr Oliver gave the red card, but was not able to give the yellow card."
Conte and Mourinho had to be separated by fourth official Mike Jones as the Italian took exception to United's heavy challenges.
"What happened on the outside for me is only (a) circus," Conte added.
"The coaches are not important."
Conte did praise the fourth official, saying: "He was very good to manage this situation, but for sure it's normal when you play this type of game."
Conte and Mourinho shook hands in the tunnel after the final whistle.
Mourinho added: "I managed to control my reactions. That's good, because this way I can be on the bench the next match.
"My players need me. It's better for me to be close to them. So I think it was good for me to control it."
David de Gea made fine saves to deny Hazard and Cahill in the first half, while United's best chance fell to Rashford, who was denied by Thibaut Courtois.
Mourinho, who again criticised the timing of the clash between Europa League last-16 legs with FC Rostov, felt United were going to win until Herrera was dismissed.
He added: "Before that I saw a game with the feeling I was going to win it.
"Everything was under control and the frustration was evident because they couldn't play the way they always play.
"With 10 men it was very difficult for us."
Chelsea advanced to the semi-final, a London derby with Tottenham at Wembley.
Chelsea beat Tottenham in December, but Spurs ended their 13-match Premier League winning streak at White Hart Lane on January 4.
"We start with one win for us and one win for them," Conte said.
"For sure it'll be an interesting game, very strong for both teams."