Mayo spent the latter half of the 2019/20 season on loan at Firhill, registering three appearances in a season that was ended prematurely owing to the virus situation.
The defender has now re-joined the Scottish Championship sided on another temporary stint, putting pen-to-paper on a season-long loan deal on Tuesday.
Jags boss McCall is delighted with having landed his top defensive target Mayo and stressed he has quality that was worth waiting for, with a season having passed since his first spell at Firhill.
McCall acknowledged the positional fluidity Mayo brings to the table but backed him to shine in his natural centre-back role at his new home.
“Lewis was my number one target to add to the defensive ranks this summer”, McCall told Partick Thistle’s official site.
“He is a player we have had to be patient about while he was needed at Rangers but he has quality that is worth waiting for.
“We had Lewis for a short time last year so we know what he’s like as a person already and he should fit in well with the rest of the guys.
“He displayed his versatility while on loan at Dunfermline last season by playing at full-back and as a defensive midfielder, but I see him primarily featuring for us as a centre back.
“We’ve got that core of the squad from last season in place but we need two or three more players to really complete the squad and Lewis brings us a step closer to that final product.
“I’m hopeful we’ll have more news about more arrivals for the squad soon.”
Mayo spent last season on loan at Dunfermline, making 26 league appearances and will be determined to add to that tally with the Jags next term as he looks to rack up more valuable first team experience.
