The 20-year-old captained the Hoops and scored a long-range goal in Tuesday's 5-0 Scottish League Cup win over Kilmarnock, despite playing at centre-back.
"He can play wherever. He's a top player," Kennedy told BBC Sport. "He still has improvement in him and he realises that himself.
"Physically he'll fill out more, technically he'll get better and as he plays more games tactically he'll become much more aware.
"For a young player he's done very well. He's got a lot of experience behind him now and you've just got to keep building on that. He's certainly up there with the top left-backs in the country."
Despite his young age, Tierney has already won four caps for the Scotland senior team.