Celtic manager Martin O'Neill admitted striker Camilo Duran has become undroppable after watching his rotated side struggle to secure a victory against St Johnstone in Perth.
The Scottish champions earned their sixth consecutive league win of the season courtesy of Mika Baur's first goal for the club since his summer transfer.
O'Neill left six-goal striker Duran on the bench for 73 minutes, but expressed dismay that his starting forward line failed to convert a series of half-chances.
With Kasper Hogh's goals drying up following a rapid start to life in Glasgow, O'Neill conceded that the Colombian international has become irreplaceable in Celtic's attack.
"Duran has just been class," O'Neill said. "He looked tired in the game against St Mirren. But I'm not surprised with the amount of things that he does for us, both with the ball, which is terrific, and also the work that he does off it."
"He's second only to Daizen Maeda in terms of closing players down," O'Neill added. "So, I wanted to try and see if we could do without him, and the answer is probably not!"
Goalscoring struggles in Perth
Despite securing the welcome victory, the Celtic manager was clearly underwhelmed with his side's poor conversion rate in front of goal during the contest.
"I thought we started off with a lot of possession," O'Neill explained. "I thought we started to create a few things. When we were doing that, it looked as if there was nobody in the penalty box for us."
"We got a bit more tempo into the game in the second half, got the goal and saw it through," he continued. "We could have scored a number of goals, but we made that look very, very difficult indeed."
O'Neill made five changes to his starting lineup, with Sam Johnstone selected ahead of Viljami Sinisalo in goal and Oliver Sorensen starting in midfield.
Johnstone produced a crucial moment in the match while the score was still level, making a fantastic reaction save to deny St Johnstone midfielder Joel Cotterill.
"He makes a great save, which is a big, big moment in the game for us," O'Neill said. "Because it could have been Saturday night all over again. The save was fantastic - a really, really brilliant reaction save. He's been a fine goalkeeper. It's just a matter of getting up to speed with things."
The English goalkeeper later suffered cramp during the closing stages, prompting a humorous reaction from his manager.
"I think he took a bit of cramp then," O'Neill remarked. "A goalkeeper taking cramp, whatever next..."
Squad depth and selection decisions
Asked if he had spoken to Sinisalo about dropping him, O'Neill confirmed he had discussed the decision with the Finnish goalkeeper, who had performed strongly prior to the match.
"Yes, he's done very, very well indeed," O'Neill said. "But you need to find out. While I do not want to use games like this, I have to find out about a number of players."
"For instance, Oliver Sorensen started the game tonight," O'Neill added. "Our main man Duran only came on in the last 10 or 15 minutes. So, it does, it gives you food for thought."
Celtic Football Club is based in Glasgow and competes in the Scottish Premiership, the top tier of professional football in Scotland. St Johnstone play their home matches at McDiarmid Park in Perth, where Celtic secured the 1-0 win.
Defensive updates ahead of Rangers clash
Defender Cameron Carter-Vickers was left out of Celtic's matchday squad entirely after feeling sore on Saturday evening following his return from a year-long injury lay-off.
However, O'Neill is optimistic that the center-back will be available for Sunday's showdown against rivals Rangers at Ibrox in the Premier Sports Cup.
"I'm hoping that he would be available, yes," O'Neill explained. "He's hardly missed a minute of pre-season and also the games. He's been out for a year and he was just feeling really sore on Saturday evening. But yes, in terms of Carter-Vickers, he should be OK for Sunday."
O'Neill praised defender Dane Murray, who deputized in defense during the match despite having his career previously disrupted by injuries.
"I've got much time for big Dane Murray," O'Neill said. "I've got a lot of time for him. I think he's got a proper career. His injuries have curtailed him for a while, but he's just coming through. I think he's got a really decent future, and things to pick up on."
Kieran Tierney also returned to action as a late substitute and is set to feature against Rangers at Ibrox in the Scottish League Cup fixture.
"It's nice to see him," O'Neill added. "We were trying to get him on the field before the end of the game. Even if he'd not got on, he'd have been alright for Sunday."
The upcoming derby match against Rangers at Ibrox Stadium forms part of the Premier Sports Cup competition as Celtic seek to continue their strong domestic form.
