"Perfectionist" Viljami Sinisalo isn't satisfied despite an impressive run in the Celtic starting line-up.
The Finland goalkeeper, afforded an opportunity by an illness to Kasper Schmeichel, has impressed in helping Martin O'Neill's side emerge unbeaten from a treacherous four-game away run in three competitions.
Sinisalo came in for the 1-0 victory in Stuttgart as Celtic won on German soil for the first time, followed by victory over Aberdeen, a league draw at Ibrox and Scottish Cup shootout win over Rangers.
But the 24-year-old feels he has more to give.
"I'm trying to be as good as I can for him to help the team win and I'm obviously trying to learn every time I play," he told CelticTV.
"I'm probably my own biggest critic in terms of I'm a perfectionist – I want to be perfect, and I want to do things better and better.
"It's just about listening to the staff, the manager, [Stevie] Woods and everyone else, and taking on board what I can do better in whatever way to help the team be successful."
Celtic head into Saturday's game against Motherwell five points above Jens Berthel Askou's side and five points behind league leaders Hearts.
Hearts travel to Kilmarnock on Saturday night while third-placed Rangers, who sit a point behind Celtic, are away to St Mirren on Sunday.
"A lot of people might write us off," Sinisalo added.
"But Celtic's not going to go anywhere, we're going to fight until the very last game.
"And that's what we've done, we've come away from those four really difficult away days, all within their own right difficult in different ways, and taken some positive results out of them, so I'm happy."
