Last night he was forced into making three changes to his starting line-up and watched on as two of those replacements scored the goals that enhanced Celtic's chances of reaching the last 16 of the competition. Further proof, if needed, that football is indeed a funny old game.
Lennon was deprived of the services of Scott Brown, the Celtic captain serving the first match of his three-game suspension, Adam Matthews, burdened by a shoulder injury, and Kris Commons, laid low with a hamstring injury. In their place came James Forrest, Biram Kayal and Teemu Pukki for their first group phase starts of the season - the young Scot confidently stroking home a first-half penalty to give his side the lead before Kayal's deflected shot early in the second period confirmed a first Celtic win of the campaign.
If the trio's inclusion was by accident rather than design, then Lennon could counter that he was due a change of luck in the Champions League this season. Brown was always going to be the biggest loss, Celtic's beating heart stuck in the stand as a result of his indiscipline against Barcelona. His absence meant another shot at redemption for Kayal, the Israeli whose stellar first season is fast becoming a distant memory.
The 25-year-old has become a fringe figure at Celtic, unable to force his way into Lennon's plans ahead of Brown, Charlie Mulgrew or Joe Ledley but this was his moment to shine as he joined Mulgrew in Celtic's two-man defensive midfield axis. It soon became apparent that the lack of game time has not taken the edge off his fitness as he roamed across the pitch with the sort of boundless energy that made him such a popular figure in his early months at the club.
He did not always look comfortable trying to contain Ajax's three-man midfield who, when in possession, were a blur of perpetual motion but did still made two vital contributions to the Celtic cause. The first came midway through the opening period when he hared back into defence to execute a perfect sliding tackle on Viktor Fischer as the Dane bore in on goal following a lightning quick Ajax counter attack. It was a hold-your-breath moment as he lunged in, the punishment for getting it wrong almost certainly a red card. His timing, though, was perfect and Celtic Park roared its approval.
There was better to come from Kayal early in the second half. Georgios Samaras' blocked shot fell to him just outside the penalty box, sitting up waiting to be lashed. Kayal instead tried to place a shot into the corner only for good fortune to intervene, his effort striking the unfortunate Stefano Denswil and bouncing into the net. His confidence duly bolstered, Kayal had two further pops on goal although both were easily saved. He departed after 70 minutes to thundering applause, with the late red card - and subsequent suspension - for countryman Nir Biton likely to enhance his chances of appearing again for the next match.
Opportunity also knocked for Pukki as Lennon rejigged his attacking options to replace the loss of Commons. Samaras moved to his more accustomed wide left slot, Anthony Stokes filled the central striker berth with Pukki tucked in behind him. Much has been expected of the Finn following his £3m transfer from Schalke and, although he hasn't weighed in with a raft of goals just yet, there have been encouraging noises made about his early performances.
Asked to play in a deeper role last night, the Finn enjoyed some nice touches in the middle of the park as he tried to link with Stokes. He didn't get into the penalty box as often might have liked but, when he did, with the game still scoreless, he passed up a great chance to put Celtic in front. The cross from Mikael Lustig was inviting but Pukki could only steer it wide of goal. It was the sort of chance Gary Hooper, underused at Norwich City, would likely have buried.
This would prove to be another big night in the tumultuous life of Forrest. A career that has had too many stops and starts for a player so young seems to be back on an upward trajectory just weeks after the player was laid low with a virus that, for a while, his manager feared might have been meningitis. A terrific strike against Hibernian showed he was back to his best, and he further enhanced his reputation here with another busy and enterprising performance.
The 22-year-old showed he had balls of steel as well, converting a penalty late in the first half after the unfortunate Denswil upended Stokes in the box. Forrest was first to grab the ball but then had to hold his nerve for the best part of two minutes while the referee attended to a spot of shoving and cajoling. Forrest kept his composure, though, to stroke his penalty past Cillessen. It was a night for the replacements to shine and they didn't disappoint.