Kasper Schmeichel, 39, has been under intense scrutiny after a series of errors, culminating in last week's slack performance in the home defeat by Stuttgart.

The 26-year-old from Finland stepped in and made six saves, in a display former Celtic midfielder Stiliyan Petrov described as "perfect".

Pat Bonner, the former Celtic goalkeeper, believes Sinisalo did enough to start against Rangers on Sunday.

"He had some very good saves and looked composed when he had the ball and read the game well," he said on BBC Scotland's Sportsound.

"It's a big decision for Martin O'Neill to make at the weekend. On that performance, I would be starting him. Give him a run in the team now."

The Celtic manager agreed several players have given him "food for thought".

"[Sinisalo] played brilliantly in the game, really well. That's the name all round the dressing room," the 73-year-old said. "He's got plenty of talent.

"Tonight, we made some changes. Some enforced, players stepped up to the plate but we didn't throw in 16-year-olds... these boys have played in the team and have shown they're capable of winning games.

"It wouldn't be a headache......