Brazilian superstar and World Player of the Year, Kaka, had knocked the ball past the then-Celtic captain on the halfway line as AC Milan broke, and the option to bring him down was there.
For a split second, Lennon braced himself for the impact he was about instigate.
But realising the Champions League last 16 tie still had 27 minutes of extra-time to go, and that he would be leaving his already-flagging team-mates to see out the match - and possibly a penalty shoot out - with a numerical disadvantage, Lennon pulled back.
The rest is history. Kaka scampered towards the Celtic goal, beat Stephen McManus on the edge of the area with a fantastic change of pace, and fired an unstoppable shot through the legs of Artur Boruc to score the only goal of the two-leg tie.
Tonight will be the first time Celtic have been back in the San Siro since that memorable night in March, 2007.
And as Lennon put his players through a training session ahead of tomorrow's Group H opener against Milan, his memories of that should-or-shouldn't moment are sure to be refreshed.
"I could have brought Kaka down as he was going through, but I would have got sent off," recounted Lennon.
"I was thinking there is another period of extra time, and I didn't want to let my team-mates down.
"I was thinking about it, though. But I was also thinking, 'He has still got a bit to do'.
"But world-class players go on and do it, as Kaka did that night."
The news his former foe is the latest name to join the list of Milan players ruled out of this game must have brought a wry smile to Lennon's face.
Some of the magic with which the Samba star was sprinkled in his heyday may have disappeared.
But the 31-year-old, who Lennon describes as 'coming home' to the San Siro after four years at Real Madrid, is still a player the Hoops boss knows to his cost can do serious damage.
Six years on from their last encounter, Lennon is once again trying to steer Celtic towards a last 16 place.
Gordon Strachan had got them there for the first time in the club's history in November 2006, and Lennon still marvels at what an achievement that was, given the manager who had replaced Martin O'Neill began his tenure a year earlier with just 13 first-team players, and the setback of crashing out of Europe to Artmedia Bratislava.
Eighteen months on, they were taking AC Milan all the way in their quest for a Champions League quarter-final spot.
And after holding the Italians to a goalless draw in the first leg at Parkhead, then again for 90 minutes in the San Siro, the dream only ended when Kaka skipped away from Lennon to score.
He recounted: "Gordon did a brilliant job, and the group we qualified from was Benfica, Manchester United and Copenhagen.
"It as a great achievement and something we were all yearning for. Then, to take Milan to the wire in the last 16, again that was great.
"Remember, they went on to win the Champions League that season, while it was uncharted waters for us. And Gordon got Celtic to the last 16 again the following year, it was a fantastic achievement.
"We had a good team, with Naka, Shaun Maloney and Kenny Miller, at the top of their game. There was also Gary Caldwell, Artur Boruc, and Paul Telfer.
"So, there was a maturity about that team because we were a little bit older."
And wiser, the successes and failures of previous European campaigns having left indelible marks on the very soul of those, like Lennon, who know their very careers can be defined by what happens on the club game's biggest stage.
Milan brought to an end Lennon's six-season sojourn with the Hoops in Europe.
By the time they played Barcelona in the last 16 the next year, he had moved south to finish his playing career.
Now he is in the enviable position of being able to put all that he has learned as a player, and, in the past three years as a manager, to good use as he tries to create another major Champions League upset.
Given the travails of Milan, who have nine players injured, a run of misfortune which has particularly afflicted their defence, there is a growing opinion among the Hoops fans they could not have picked a better time to take on the Rosinerri.
However, Lennon has been down this road often enough to know that, when a team like Milan look to be at their most vulnerable, they can call upon top stars to dig them out of a hole, just as Kaka did in 2007.
So, while the defence may be depleted, the attack can still look to such as the physically-imposing and unpredictable Mario Balotelli to weave a bit of magic.
Another of the missing Milan stars, Stephan El Shaaraway, has already boasted that a Hoops side which conceded cheap goals to Shakhter Karagandy will not contain the striking power of the Serie A giants.
Reassuringly for Lennon, his back-line has looked much more secure since that bad night in Kazakhstan in the play-off, and the combination of Efe Ambrose and Virgil van Dijk is improving with every game they play together.
Only a deflection prevented the Nigerian and the Dutchman from claiming a clean sheet against Hearts at the weekend, and Lennon will be tempted to go with them as his central partnership tomorrow night.
The manager said of the pairing: "It is early days, but they have been very good. We can always throw Mikael Lustig in there as well, but I am pretty pleased with the pair of them so far.
"The loss of Steven Mouyokolo is big as he would probably have played on Saturday, and he would have been a decent man to have, particularly away from home in games in Scotland.
"But Efe has started the season in great form, and Virgil is beginning to find his way now."
Lennon concedes that games like tomorrow night's, and the five other Group H games which follow, will provide the acid test for everyone in his squad.
It is a quantum leap from SPFL Premiership to Champions League games, but Lennon is confident his Bhoys are prepared for what lies ahead.
"Yes, it's a big jump," said Lennon. "But, you have to look at Ambrose, Brown, Samaras, Ledley, Mulgrew, Matthews, Lustig - they are all international players who have played at the highest level.
"Guys like Sami have got around 60 caps for their country. So, they have played against top players before, and played at the tempo and against the quality.So, nothing will faze them."
The bulk of the squad have also proved themselves good enough to qualify from a tough group for the last 16.
Lennon is not naive enough to claim they will do so again, but he does believe they are well equipped to give it a go.
"We had 10 Champions League group stage rookies last year, and they did okay," he said.
"So, I'm not over confident, but I am confident we can really compete in this group again."