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."
Meanwhile, Lennon says they will make a fresh approach to try and land Teemu Pukki and hasn't given up hope on landing Alfred Finnbogason.
The Hoops failed in an initial bid for Finnish striker Pukki on Thursday, with Schalke 04 knocking back their approach.
Lennon said talks were "ongoing" and said he hoped to land the player to beat Monday's Champions League signing deadline, where they can add one player to their squad ahead of their play-off round ties with Shakhter Karagandy.
The Celtic boss revealed that he had watched Pukki in action for Finland against Slovenia on Wednesday night.
Celtic had also been linked with a swoop for Heerenveen's Alfred Finnbogason and Lennon said that they may still make a move for the Icelandic international, even if they were successful in signing Pukki.
Lennon's side have previously confirmed an interest in Finnbogason, who is reportedly valued at just over £4m.
Pukki, 24, has a year left to go on his deal with the Bundesliga side and has not enjoyed regular first team starts since moving from HJK two years ago.
He started his career with FC KooTeePee before moving to Sevilla in 2008, making two appearances for the top team before returning to his native Finland with HJK Helsinki.
After 13 goals in 29 domestic appearances across two seasons, as well as five in six European matches, a move to Germany with Schalke 04 followed in 2011 in a £1.3m switch.
Pukki has struggled for playing time in the Bundesliga, starting just seven of his 36 appearances for the club over two seasons, scoring on eight occasions.
He featured more regularly in the Champions League last season with Schalke, starting three of his five games without finding the net.
At international level, Pukki has scored six goals in 24 appearances and was on target in a World Cup qualifier with Spain in March.
Finnbogason scored 24 goals in 33 Eredivisie games last season and has scored three in two appearances this campaign.