The long-serving Sweden right-back left the Hoops as a free agent last month after seven years of service.
Lustig, who turns 33 this year, won eight Scottish Premiership titles in a row and his exit was mourned by many Celtic supporters.
Kayal played alongside the new Gent defender at Parkhead for three years, and the Israel international respects his old team-mate's decision to take on a new challenge.
“I’m sad to see Mikael leave as he has been one of the best right backs in Scottish football but you need to respect his decision to take on a new challenge," he told The Record.
"He still has the quality and has performed unbelievably well and I wish him all the best.”
Lustig's replacement looks set to be a man who Kayal knows well - his international team-mate Hatem Abd Elhamed, who is closing in on a £1.6 million move to Glasgow.
Not only that, but Kayal, now a Premier League player with Brighton, admitted in the same interview that he recommended Celtic to the 28-year-old defender.
Lustig was earning around £24,000 per week with the Bhoys, according to The Daily Star. That indicates that he was a big player for the Scots and Elhamed will have big shoes to fill.
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