United go to Stamford Bridge with a nine-point deficit on third-placed Chelsea - a gap few predicted when the sides played out a goalless draw at Old Trafford back in August.
In the aftermath of that game Jose Mourinho offered no excuses for a cautious approach, drawing a contrast between the "babies" in his squad and the champions' strength.
But Chelsea's progress since, and a run of three January defeats for United, means it is David Moyes and his squad under scrutiny ahead of Sunday's return fixture.
Silvestre, who won five Premier League titles and the UEFA Champions League during nine years at United, told Sky Sports News it is time to come out fighting.
He said: "Lack of consistency has been the problem.
"We've seen some good performances, especially in the Champions League and at Old Trafford against Arsenal, and we've seen some lows.
"There is a lot of pressure on the new management, but you have to deal with it. Sunday's game is a good opportunity to show you've got the character to come back.
"You don't want them to lose, that's for sure. They need to stop losing ground behind Chelsea."
Last weekend's victory over Swansea meant Moyes avoided the unwanted tag of presiding over United's worst Premier League-era run, and Silvestre took encouragement from that result.
He said: "I hope going off the Swansea second-half performance the team would get enough confidence for a positive performance at Stamford Bridge. Being an ex-United player I will support the team this Sunday."
Watch Manchester United take on Chelsea as part of our Super Sunday double bill, live on Sky Sports 1. Kick-off at Stamford Bridge is at 4pm.