The Scottish champions face Aberdeen in the early kick-off tomorrow before travelling to Kazakhstan for Tuesday's crucial play-off qualifier against Shakhter Karagandy.
But the Parkhead boss was left sweating on the fitness of three of his players as skipper Scott Brown and winger James Forrest started against the Auld Enemy at Wembley, while defender Charlie Mulgrew was a second-half substitute as Gordon Strachan's men lost 3-2 in London.
Thankfully for Lennon, the Celtic contingent returned to Scotland unscathed, but he admits the timing of the game so close to the first-leg clash with the Kazakhs was a worry.
He said: "It was a disaster for us in terms of the games we have. We've got a 12.30pm kick-off against one of our biggest rivals and then a huge game on Tuesday half-way across Europe.
"But it is the same every season, when it seems you have these international friendlies before some of the associations have even kicked a ball in anger.
"We only got a few of the players back today so it's always a difficult week, the international week, for us. They look in good spirits, the majority of them and we will assess how they are."