Celtic reportedly brought in around £25 million for Kieran Tierney, with the full-back still yet to make his Arsenal debut.
Some Celtic fans were frustrated when Tierney left Parkhead to join Arsenal in a £25 million (BBC Sport) deal.
But Lennon feels that Celtic got good money for the left-back, who is still waiting to make his Gunners debut.
“‘We lost some quality players and they are difficult to replace,” Lennon admitted.
“But eventually these guys will put their own stamp on the club. Greg [Taylor], for example, has been one of the best and most consistent players in the league for the past two or three seasons.
“I think overall we are healthy. We have spent some money and brought some quality players in shrewdly.
“We’ve also made a really good sale of a top player and we got top dollar for him. It has been a very good window. I think we are strong.”
Celtic have brought in two left-backs this summer to try and cover for the void of losing Tierney.
The Bhoys have signed Boli Bolingoli, who has started this season at Celtic’s first choice left-back, and Greg Taylor more recently.
However, Tierney was arguably Celtic’s best player, and his departure unquestionable hurts Lennon’s side.
Tierney has made a slow start at Arsenal due to injury, and still has not made his first team debut for Unai Emery’s side.
When Tierney does make it back to full fitness he is expected to become a starter at the Emirates Stadium.
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