Celtic kick off their European campaign in Belfast on Wednesday night, less than eight weeks after closing their season with a William Hill Scottish Cup final victory over Hibernian.
Lennon's preparations have been far from ideal - Celtic conceded 12 goals as they lost all four of their friendlies during a stint in Germany.
The former Northern Ireland captain has seen midfielder Victor Wanyama leave for Southampton and fears striker Gary Hooper, who has been struggling with a groin problem, has played his last game for the club as he seeks to join the Kenyan in England.
Nigeria defender Efe Ambrose will miss the clash on the artificial surface at Cliftonville's Solitude ground after being given extra time off following the Confederations Cup.
Welsh pair Joe Ledley and Adam Matthews are expected to miss out through injury while trialist defender Steven Mouyokolo has still to sign a contract, and the likes of Scott Brown, James Forrest, Charlie Mulgrew and new signing Virgil van Dijk have all missed part of the friendly action through injury.
Lennon has already raised the prospect of facing extra-time against Cliftonville at Celtic Park in the second leg and he admits they will need to dig deep against the Danske Bank Premiership champions.
Lennon told Celtic TV: "It's so early, it's a harsh reality of where we are. We won the cup final at the end of May and we are back in on the 24th of June. It's been staggered and a bit disjointed because we have had a lot of injuries as well. Matthews, Ledley, Twardzik and Hooper have hardly featured and obviously we have lost Victor.
"They are the ups and downs you have to cope with during pre-season but I don't think you'll see us anywhere near our best for another two weeks or so."
Celtic closed their German trip with a 3-0 defeat against second-tier side Union Berlin on Friday night and are back at Lennoxtown on Monday before flying to Belfast the day after.