The pair were both absent for the 1-0 Tannadice triumph but could play vital roles for Gordon Strachan's side in our World Cup qualifying double-header with Belgium and Macedonia.
Lennon said: "We had to patch a few up - Joe Ledley, Adam Matthews, Kris Commons - from Wednesday night. Mulgrew had a bug, Forrest had a sore ankle so he wasn't fit."
He added: "Yes, I think they will be fine for Scotland. James took a heavy one on the ankle towards the end of the game on Wednesday night and didn't recover on time to play on Saturday.
"Charlie had a stomach bug, he didn't feel well on Saturday morning so we decided not to take any chances with him."
If Mulgrew and Forrest do recover in time to join up with the national squad ahead of Friday's glamour tie against the Belgians, they are likely to be joined by Parkhead skipper Scott Brown.
Brown was one of the Dark Blues' key men in their agonising defeat to England at Wembley and Lennon has hailed the midfield star.
He said: "I might take the Scotland game in. Scott is playing very well. He is injury-free and he is back to his very best. He is a great captain and long may that continue."
Meanwhile, West Brom pair James Morrison and Graham Dorrans have both withdrawn from the Scotland squad.
Morrison was substituted with a groin injury during the Barclays Premier League defeat to Swansea.