When Celtic signed Sam Johnstone on loan from Wolves at the end of the transfer window, his arrival didn’t exactly set the pulse racing among supporters.On social media and radio phone-ins, many fans questioned the wisdom of signing a 33-year-old goalkeeper who hasn’t played a huge amount of football these last few years.Even though Johnstone has four England caps to his name, all of which yielded clean sheets, the overriding feeling among punters was one of indifference. A collective shrug of the shoulders.With all of that in mind, it came as quite the surprise when Martin O’Neill pitched Johnstone in for a debut in the 1-0 win over St Johnstone in Perth in midweek.O’Neill clearly sees a goalkeeper who can add value to Celtic with his quality and experience, even if some fans would still struggle to pick Johnstone out in a crowd.It leaves the Celtic boss with a major selection dilemma heading into Sunday’s Premier Sports Cup quarter-final clash with Rangers at Ibrox. Will Sam Johnstone or Viljami Sinisalo get the nod to face Rangers?Does he stick with Johnstone, or hand the gloves back to Viljami Sinisalo?’I haven’t made my mind up at all,’ he said on Friday. ‘It’s great to have the two of them.’Viljami has done exceptionally well for us and it was just, again, an opportunity to see what Sam can do now.’What he could do a couple of years ago was fantastic, what he can do now might be a totally different picture.’The bearpit of Ibrox could well be a brutal and unforgiving arena for any Celtic goalkeeper. Any mistakes could be ruthlessly exposed.It’s certainly not the type of environment or fixture that would lend itself to any kind of experimentation.Whichever goalkeeper O’Neill picks would give a clear indication as to who the No1 will be moving forward into the rest of the season.The smart money suggests that Johnstone might well get the nod. Why else would O’Neill have blooded him in midweek?Even accounting for the fact that cup ties often see the back-up goalkeeper play, going with Sinisalo, only to then go back to Johnstone for the league clash with Rangers next week would seem an erratic choice. Sam Johnstone kept a clean sheet on his Celtic debut against St JohnstoneThis is a period that calls for stability, with the Europa League campaign getting under way against Ferencvaros on Thursday night.Johnstone performed well against St Johnstone in midweek, making one decent save in particular. He looks a safe enough pair of hands, perhaps even an upgrade on Sinisalo.Former Celtic captain Scott Brown spoke in midweek about the goalkeeping situation and backed Johnstone as the man to keep the jersey long-term.All of this could seem harsh on Sinisalo. Has he really done anything that would warrant being dropped?Granted, he could probably have done better for a couple of the goals against LASK Linz in that shambolic night in Austria, but he was far from alone in having a poor game on that occasion.When it became clear that Kasper Schmeichel patently wasn’t fit last season, Sinisalo stepped up and performed well over the rest of the campaign.Goalkeepers live with the knowledge that form is judged in snapshots and that one error can potentially cost them months out of the team.Sinisalo has not supplied that error thus far. There have been no major howlers, only a feeling that he might have done better in some moments.To sideline him solely because a more decorated alternative is available, one with a few England caps and mileage in the Premier League down south, risks looking reactive rather than considered.Competition is, of course, healthy and O’Neill has been clear that keepers should face the same scrutiny as outfield players. Johnstone was signed precisely to provide that challenge to Sinisalo.At this level, particularly in an Old Firm match, managers are entitled to pick the man they believe gives them the best chance of survival and progression.Experience often counts heavily when the stands are bouncing and every cross feels like an aerial bombardment.And there will be plenty of those this afternoon. A key part of Rangers’ gameplan in attack under Derek McInnes has been to get the ball wide and get crosses into the box.Sinisalo would be entitled to feel harshly treated if he ends up being bombed out, but these are the decisions by which managers live and die.At 33 years of age, O’Neill has spoken about Johnstone still having plenty of miles left on the clock. The key will be getting him back to the form that saw him become a member of Gareth Southgate’s England squad. Sinisalo has been a steady performer for Celtic since replacing Kasper SchmeichelCeltic are actually the 12th club of Johnstone’s professional career. He has been around the block, all right, and learned his trade.He came through the youth ranks at Manchester United at a time when the likes of Edwin van der Sar and then David de Gea were the goalkeepers at Old Trafford.United gave him the education but ultimately not the games or the opportunity. What followed was a classic apprenticeship of loans: Scunthorpe, Walsall, Yeovil, Doncaster Rovers, hometown Preston North End and a lengthy, formative spell at Aston Villa under Steve Bruce.At Villa, he played regularly in the Championship, reached a play-off final and learned what first-team football actually felt like.In 2018, he left United permanently for West Bromwich Albion in a deal worth around £7million. Johnstone helped the Baggies win promotion in 2019-20 and then delivered a standout Premier League campaign the following season.West Brom went down but Johnstone was named both Supporters’ and Players’ Player of the Year. Big saves against the likes of Manchester United and Liverpool earned him national recognition.Southgate called him up in March 2021 and his debut came against Romania in June that year at the Riverside Stadium: a 1-0 win and a clean sheet. He was part of the Euro 2020 squad that reached the final. Celtic goalkeeper Sam Johnstone in action for England back in 2021Four senior caps in total, four clean sheets. The last of them came against Australia at Wembley in October 2023.Crystal Palace took him on a free transfer in 2022. He established himself as number one, only for injuries and the arrival of fellow United graduate Dean Henderson to push him down the pecking order.Wolves paid a reported £12million for him in the summer of 2024. Two seasons at Molineux brought limited opportunities, an injury and eventual relegation. By the start of this campaign, he was surplus to requirements.That’s when Celtic came calling. A season-long loan was agreed and, having been barely in the door five minutes, he could now be set for an Old Firm debut.Johnstone has already spoken about longevity, pointing to Craig Gordon playing into his forties and saying he would love a similar run.The loan move to Glasgow is an opportunity to play regularly again, to remind people of the level he reached in that West Brom season, and perhaps even to put himself back on the England radar.What unfolds at Ibrox on Sunday will not settle everything, but it will crystallise the choice made by O’Neill. Whoever starts will face the intensity that only this fixture produces.Whatever the call, one of them will be disappointed. Whether he goes with Johnstone or Sinisalo, this is the burning question facing O’Neill as he prepares for another crack at an Old Firm derby.Click here to visit the Scotland home page for the latest news and sport