Nemaja Matić was man-of-the-match in Chelsea's 2-1 win on Saturday over Liverpool.
Matić has been invaluable to Chelsea in his second stint with the club.
"He is the best player," said José Mourinho.
"He was signed in the most difficult market. Which is for the players who are coming in mid-season, so the last half of the season was for him to improve, not adaptation, as he was a Chelsea player before, but to improve.
"At this moment he is a giant, not for his size but for the way he plays. The man is a giant."