The 17-year-old flattened Dutch World Cup star Wesley Sneijder while playing in the Antalya Cup in Turkey in January.
Though it also confirmed the young midfielder still had to learn discretion, the Celtic boss was impressed enough to put him into his first team just a couple of months later.
Lennon said: "I'd seen Liam play development games when he was 16, and he came into the first-team environment and didn't look out of place.
"Physically, he's got a bit to do, but he's a very fit boy, composed, and can see a pass.
"He's also got a very good engine on him and has taken his opportunity very well.
"He will put his foot in, too.
"We were playing in Turkey against Galatasaray and I said: 'Look, you might need to do the dark side of the game here. If you feel they are breaking on us, just commit a foul and let us get reorganised'.
"He took it far too literally. Five minutes into the second half, Wesley Sneijder's breaking and he just walloped him.
"I thought, 'Well, at least he's listening.' He just needs to be a bit more subtle about it."
Henderson is learning quickly, and the son of former Partick Thistle midfielder Nicky may not be the last in the family to make a big impression.
The Young Player for the Month for March explained: "I've got two wee brothers, Jamie who's 14 and Ewan who's 16, and they are both probably better than me.
"Ewan's got everything. He's at Celtic Under-15s and my other brother just plays boys' club, but he's a player as well."