Roy Hodgson revealed that, with England having safely secured their passage to Rio next summer, he will look to give Forster a game, and Lennon has told the keeper maintaining his European form could be the key to him getting the nod for Brazil.
Joe Hart has been jittery for both club and country, but he remains the number one choice.
However, Forster has done enough to merit inclusion in the squad and Lennon expects continuing to excel against Ajax, AC Milan and Barcelona will keep the stopper firmly at the forefront of Hodgson's mind.
"What he needs to do now is keep his focus on his club football and keep his level of performance high and it then becomes very difficult for Roy not to pick him," said the Celtic manager.
"He has to keep playing, certainly at Champions League level and keep producing the performances he has done over the years. He is at a disadvantage, I think, to the rest of the players who are in the squad, but he is more than capable of playing for England.
"I think without the Champions League he may not have been picked for England. That's the reality of it. The quality of his goalkeeping at that level is exceptionally high and he has caught a lot of people's attention, including the England manager.
"We have another four games left in the group, possibly another two if we can qualify, so he has plenty of opportunity to keep reinforcing his position in the squad."
There were a number of buoyant players returning to club duty - and none more so than Anthony Stokes.
The striker is back in the Republic of Ireland fold after falling out of favour under the now- departed Giovanni Trapattoni. But, like Forster, Lennon has urged the striker to maintain his early-season form in order to keep himself involved at that level.
"He was picked for both games, which was brave, and I think he did very well in both outings. I watched the game against Germany last Friday where they were always going to be up against it, but he did reasonably well and, by all accounts, did well on Tuesday," he said.
"It is testimony to the form he has shown this season. But I don't want it to be a short-term thing. He has to maintain his consistency for us to keep getting picked at international level."
The Scottish lads in the Hoops dressing room also had a spring in their step this week and, for Lennon, the influence of Gordon Strachan on the national team is there for all to see.
"I had two years playing under him and a year-and-a-bit coaching under him and I learned a lot off him," said Lennon. "He did wonderful things here, amazing things really and I think international football suits him.
"The team comes first, he is the manager, and he gets the respect of the players. I think his man-management is excellent and what he does on the training ground appeals to players as well. He gets his message across succinctly and he has always been very good on the training ground."