Kieran Tierney has gone on to captain Celtic
Emilio Izaguirre wants to help Kieran Tierney fulfil his potential and "become the best left-back in the world" after returning to Celtic.
Tierney came through the youth ranks in 2015 to eventually oust Izaguirre from the Glasgow side's starting XI.
The Honduran left Scotland a year ago to pursue first-team football in Saudi Arabia but returned on Friday to sign a one-year deal.
"I'm very happy as Tierney is my boy," Izaguirre told the Celtic website.
"I always tried to stay in touch with him and help him - and I'm happy to help him progress. I want to help him become the best left-back in the world.
"He wanted to be a big player. He needs to continue to work hard and keep doing the things he did last year and he can be the best player in his position in the world."
Izaguirre rejoins Celtic
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Izaguirre, 32, only played 18 matches in his last season with Celtic before heading to Al-Fayha last summer.
His path to regular game time is still impeded by Tierney, who has since gone on to captain both Celtic and Scotland.
However, the Honduras international is prepared to be patient.
"It was difficult for me as I wanted to try and play more, but, after one year, I understood that I never wanted to leave and it's more important that I try and help the team at Celtic," he said.
"For me, it's important to help the team in any way I can, whether I play or not.
"My focus is to play any minutes when the gaffer gives me the opportunity and always to be positive for the team."
Kieran Tierney captain Scotland against the Netherlands last year