Influential City playmaker Silva scored a late winner last time out against West Ham to preserve an eight-point lead for Guardiola over Mourinho at the top of the Premier League table.
But the Spain international has not travelled for Thursday's UEFA Champions League game against Shakhtar Donetsk, where Guardiola is expected to rest other key stars given his team have already secured progress to the knockout stages as Group F winners.
The former Barcelona coach told a pre-match news conference that Silva was a doubt for Sunday's game at Old Trafford, although he failed to specify the nature of the 31-year-old's complaint.
Speaking after Tuesday's 2-1 win over CSKA Moscow, Mourinho was not buying it and grouped Guardiola's claims with those of Arsene Wenger, the Arsenal manager who said Alexandre Lacazette would not face United last weekend before he promptly played and scored in the Emirates Stadium thriller that the visitors won 3-1.
"The truth is Eric Bailly, no chance for the weekend, Phil Jones a chance, [Marouane] Fellaini a chance, Zlatan [Ibrahimovic] a big chance and [Nemanja] Matic is injured but will play for sure. [Michael] Carrick no chance," Mourinho told a news conference
"I'm telling the truth, he's injured but will play for sure. No stories of Lacazette or David Silva. All the truth."
Speaking to BT Sport, Mourinho maintained his theme and claimed United are "a bit more humble" that their rivals.
He also picked up a thread from earlier in the season – his perception that opponents complain about injuries in a manner that he does not.
"No, we have no injuries," he said. "Our opponents have all these issues. They have a big issue but in the end everybody is ready to play.
"They have phenomenal organisations. We are a bit more humble.
"When we have a problem, we have a problem. When players are injured, they are injured. I tell you the truth."