According to Calciomercato.com, he took issue with being asked about the Brazilian: "Why are you asking about Willian and not [Eden] Hazard at the start of the season, and not Pedro the same? They have the same situation."
"My players must be happy to stay in Chelsea and to play for Chelsea and to play for our fans. They must be happy if they start the game, or if they stay on the bench and come on.
"I think I have clever players to understand the situation and accept it. Hazard, at the start of the season, accepted the situation to stay on the bench before finding the right form. It's the same for Pedro, for Willy [Caballero], for other players.
"When you are in a great team, you have to accept this and, at the same time, you must be happy to stay in a great team."
Willian has only started 11 of his 21 appearances this season and has completed 90 minutes on less than half of those occasions.
The Brazilian duo are both represented by agent Giuliano Bertolucci, who also "played a key role in negotiating" their compatriot Paulinho's Barcelona transfer in the summer.
Willian is a divisive figure among some Chelsea fans after he suffered a dip in form. However, as Goal's Nizaar Kinsella noted, it seems negative assessments of the winger were premature given his recent performances:
He grabbed Chelsea's equaliser against Liverpool in their 1-1 draw, albeit unintentionally, and prior to that, he played a key role in the 4-0 win over Qarabag in the Champions League.
Kinsella shared his numbers from that game:
That he put in such a showing in Azerbaijan was important as it allowed Eden Hazard to come off early to keep him fresh for the Liverpool clash after a 5,000-mile round trip, which showcased Willian's usefulness to the squad.
ESPN FC's Liam Twomey noted his Champions League scoring record:
Willian may not be capable of achieving the same heights as some of his team-mates, Hazard in particular, but along with Pedro, he represents a solid option on the right of their front three or tucking in behind Alvaro Morata.
He's worth keeping at Stamford Bridge, and if he can continue to offer reminders of his talent as he did against Qarabag and Liverpool, he might find himself playing a more prominent role in the team.