Martin O'Neill 'not sure what to make of' Celtic, so what are issues?

His "laborious" Celtic side made it six wins out of six in the Scottish Premiership by sneaking by St Johnstone, but his much-changed side far from had it all their own way.

After handing a debut to on-loan Wolves goalkeeper Sam Johnstone, a first Celtic start to midfielder Oliver Sorensen and a rare run-out for centre-back Dane Murray - in addition to recalling winger Sebastian Tounekti and striker Kasper Hogh - the veteran manager would have hoped to have had a better idea of new-looking squad as he "juggles" players and positions.

Speaking after Mika Baur's first goal for the club delivered victory, O'Neill told BBC Sport Scotland "I'm not sure what to make of it, really," while admitting to Sky Sports "we're still well short of it".

With the first Europa League game - at home to Ferencvaros next Thursday - sandwiching a double-header against Rangers, in the Premier Sports Cup on Sunday before the league a week later, it appears O'Neill has some issues to address for a mammoth week.

Despite the tasty triple-header which awaits the reigning champions, O'Neill was insistent on the importance of the match at McDiarmid Park in prioritising their title defence.

It made his fives changes even more surprising. Among them, the omission of Camilo Duran was the most surprising given his blistering start in a Celtic shirt.

Much of the pre-match chat centred on whether the returning Hogh and Duran would play together as strikers or if the Colombian would shift back out wide. No one really considered him being dropped to the bench. And it appears unlikely O'Neill will be tempted to do so again.

"Our main man only came on in the last 10 or 15 minutes, so it gives you food for thought," the Northern Irishman said after his side failed to add to their tally despite upping the ante after Mika Baur's goal early in the second half.

"[Duran's] just been class. He looked tired in the game on Saturday, but I'm not surprised for the amount of things 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. So, I wanted to try and see if we could do without him, and the answer is probably not."

How much will Celtic miss Asian Games-bound Yang?

As delightful as it is to have a diamond like Duran, O'Neill won't want his side to become overly dependent on the 24-year-old in the way they previously did with the now departed Maeda.

Hogh, a poacher, is the polar-opposite to livewire Duran and, with the service as poor as it was from the wings on Wednesday, it was always going to be a night of struggle for the Dane.

He touched the ball just twice in the box before the break, but O'Neill did hint at the club's record signing needing to do more. "You just can't put the ball on a plate for people," he said to Sky Sports. "They have to make room for themselves in the penalty box to try and score a goal."

Yang Hyun-jun was also missed after a glittering start to the season, but the drop-off in confidence, quality and delivery from the South Korea winger to Tounekti was staggering, with former Scotland international James McFadden calling his performance and decision-making "safe" at half-time.

"He likes to come inside, that's pretty positive until the last part," he said on Sky Sports.

"He's got a big problem in his starting position, where he receives the ball, he's always in the eye-line of the defender.

"He's frustrating to watch because he's quick and sharp with good feet, but he's desperate to come inside and never wants to take the risk of going down the outside."

Countless times in the first half especially, Hogh cut an exasperated figure after pulling and pealing away from defenders before not being found by his team-mate.

Celtic lead way from Rangers after narrow wins

The more things change, the more things stay the same. James Forrest starring against St Johnstone.

With 12 to his name, the 35-year-old has scored more goals against the Perth side than any other team in his long and distinguished Celtic career.

He didn't add to that tally but his cameo performance had McFadden calling for the experienced winger to start against Rangers on Sunday.

Forrest flashed a handful of enticing balls across the face of goal, but there were just no takers. He wasn't shy at taking a shot when the opportunity presented itself either.

"I think Forrest starts at the weekend," McFadden added. "He gives you far more in that position."

It's an interesting debate with Duran in the conversation too, if he is not deployed through the middle.

On the right, Haissem Hassan's final ball was not much better, but his decision making was more positive as he set up Baur's simple finish.

In principle, yes. In practise, perhaps not yet. In short, Celtic looked like a side who had made five changes.

Yet they faced a St Johnstone team who made four of their own - including a first start for Joe Cotterill - who forced Johnstone into a superb save - and a debut for on-loan Hibs midfielder Josh Campbell.

Pre-match, O'Neill admitted he "had no idea" what midfielder Sorensen was capable of. He may yet still be wondering as the game seemingly passed him by.

It was a bold call to leave Duran and fellow goal-threat Benjamin Nygren - who replaced Sorensen with over 20 minutes to go - on the bench but it did - just - pay off, with the influential pair enjoying a little rest before the Rangers tie.

"I know the results have been fine, really fine, but when we get players up to speed, that'll be great," O'Neill reiterated.

"I think that'll take a few weeks for players. In the meantime, the most important thing is to try and keep your head above water."