Matic missed the 3-1 win at Manchester City last time out with a muscular injury, with Fabregas impressing when he stepped into the side for only his second league start of the season.
Conte has reiterated he wants the former Arsenal and Barcelona midfielder to stay in the January transfer window, but faces a dilemma over whether to keep him in the team for the Premier League clash with West Brom at Stamford Bridge.
"Matic is now fit," Conte said at his pre-match media conference.
"He trained with us from Tuesday and I also have Saturday to evaluate the physical and mental situation of every single player and then to decide for the line-up on Sunday.
"About Cesc, I have already replied in the previous press conference. Cesc is a good player, an important player in my squad. I want him to stay here.
"I hope to have these difficult [selection] decisions in every game. It means that I have great competition and this means the level in our squad is improving and raising.
"I think Cesc played a good game against City and took the opportunity from the first minute. He played very well.
"Now for the next game I have a choice of four midfielders: Matic, [N'Golo] Kante, Fabregas and [Nathaniel] Chalobah.
"We have to take the best decision for the team. If there is great competition this is very important.
"If I haven't got a problem to take the decision and always put the same line-up it is not good."
The only players set to miss out for Chelsea against Tony Pulis' side are John Terry and Oscar.
Conte added: "We have John recovering from his injury - he is not back for this game. Oscar is sick.
"The other players we can recover, it's important to see on Saturday that they are all able to play and then I'll decide the starting XI."