The Dutch centre-back joined the Scottish champions in 2013 from Groningen for a reported fee of £2.6million and Lennon quickly realised the Bhoys had snared a talent.
"I was really surprised that no one came in earlier for him when he was at Celtic," Lennon told BT Sport of his first day with Van Dijk.
"After one day I pulled him in after training and said to him 'Look, you're not going to be here long, so enjoy yourself.
"He was just that good. And I couldn't believe our luck that we had got him from Groningen for €2million. He had everything.
"Pace, great physicality, technique and superb in the air in both boxes."