Chelsea head coach Enzo Maresca has conceded that Moises Caicedo deserved to be sent off during Sunday's 1-1 draw against Arsenal in the Premier League.
However, the Italian questioned why a similar incident went against the Blues earlier in the campaign, raising concerns over inconsistency regarding refereeing decisions.
Once Chelsea were reduced to 10 men late in the first half, the advantage was with Premier League leaders Arsenal, who were sensing an opportunity to move nine points clear at the top of the table.
Instead, Trevoh Chalobah put Chelsea in front soon after the restart, and it took a Mikel Merino equaliser 11 minutes later to earn the Gunners what would have felt like a disappointing share of the spoils.
Maresca addresses Caicedo red card in Chelsea, Arsenal draw
Speaking to Sky Sports after the match, Maresca was quick to acknowledge that he had no complaints over Caicedo being handed a red card for a studs-up, late challenge that made connection with Merino's ankle with force.
Nevertheless, Maresca compared the tackle to one made by Tottenham Hotspur midfielder Rodrigo Bentancur on Reece James in their own recent London derby, a challenge that only led to a yellow card.
He said: "I think he red card is the red card. I struggle to understand the different ways to judge.
"What about Bentancur to Reece? Why is one a red card and one isn't? I think it's a red card tonight, it's clear. Why the difference? Is what it is.
"Moises is always the same way. Top player for us. The desire from him is to try and win the game.
"It's football. It's between Chelsea and Arsenal. You have to double the effort, that is the most important thing. We didn't change a lot on the ball. We tried to go to Liam. In open play, the idea was exactly the same."
What next for Chelsea and Arsenal?
Arsenal end the weekend with a five-point lead at the top of the standings, with Manchester City having moved into second and ahead of Chelsea.
Both the Blues and Gunners are in action on Wednesday, with Maresca taking his team to face Leeds United at Elland Road and Mikel Arteta's side playing host to Brentford.
Chelsea will be without Caicedo for the next three matches due to suspension, the Ecuador international also missing games with Bournemouth and Everton.