Bruno Fernandes will play for Sporting Lisbon against Benfica on Friday night.
Portugal international Fernandes is closing on a move to Manchester United after the Red Devils made him their No.1 transfer target this month.
Ed Woodward, United’s executive vice-chairman, held discussions with Sporting president Frederico Varandas last Friday at the club’s Mayfair offices, before negotiations continued this week.
Fernandes has agreed his part of a deal at Old Trafford, while Sporting - in need to pay debts to the tune of £40million this month - are hoping to land £50million plus add-ons potentially reaching £65million, for the Portuguese international.
Those talks are still ongoing, but a breakthrough is believed to be within reach ahead of a potential announcement on Monday - despite Ole Gunnar Solskjaer remaining silent on the situation.
Now Sporting boss Silas has confirmed that Fernandes will start in Portugal’s most historic fixture, in what is set to be Fernandes' finale at the Jose Alvalade Stadium
"The only certainty I have is that Bruno will play [in the derby]," said the Sporting boss at his pre-match press conference on Thursday.
"We prepared the game with him, trained very well. He is the most valuable player in the league and last year he was.
"I've heard some people talk about money. He isn't worth the numbers they refer to, but he's worth a lot more.
"In addition to attacking, he kills himself to defend. There is no player doing what he does in Portugal and there was nobody last year either.
"When we have such a player, it is normal for a lot of people to want it. Only if there is a catastrophe will there not be.”
Silas, who once had a spell in English football with Wolves, also added that it will take three players for Sporting to replace their talisman.
"In Portugal there are good players, but to replace Bruno we need three," he declared.
"I don't know if we are going to get some dynamics, there is no player who can replace him."
Benfica currently lead the Portuguese league, having dropped just three points in their opening 16 matches.
Sporting by contrast are in fourth spot, 16 points behind their bitter rivals, having already succumbed to five losses in their opening 16 outings.