Celtic got the win against Falkirk and, after what happened in Austria, that was the absolute minimum required.

There was plenty to like in the first half as well. Camilo Duran looked dangerous through the middle, Haissem Hassan showed flashes of what he can bring and Celtic could quite easily have put the game beyond Falkirk before the break.

But watching the second half, it was difficult not to think back to LASK.

There are two things beginning to concern me about this Celtic team. The first is the quality O’Neill has available when he looks towards his bench.

Celtic started with Yang, Duran and Hassan as their front three. By the closing stages, James Forrest, Tounekti and Osmand were tasked with seeing the game out in attack.

That’s a considerable change in the level of threat Celtic carry.

This isn’t about having a go at young players or those being asked to come on and do a job. The point is that Celtic should have enough quality throughout their squad that substitutions don’t completely change the complexion of the team.

Falkirk scored and suddenly Celtic needed to find another gear. Instead, the opposite happened. The attacking threat faded and the game became far more uncomfortable than it ever needed to be. You then have to account for injuries. Kieran Tierney has suffered a hip injury int he Falkirk win and now the hoops look set to go into a game against Aberdeen midweek with Liam Scales at left back. Where is the depth?!

We’ve already seen the consequences of that in much more painful circumstances.

Celtic were running on empty after an hour against LASK. The legs disappeared, LASK could see it happening and O’Neill didn’t have enough on the bench to change the direction the game was heading.

That brings me to something I find even more concerning.

Why are Celtic looking so tired?

Hassan is exempt from this discussion. He’s still getting himself properly fit and that will take time. I’m talking about players who have had a full pre-season and should, by the end of August, be approaching the levels required to play twice a week.

Yet we saw Celtic physically wilt in Austria and there was another noticeable drop against Falkirk.

What are they doing on the training ground?

It’s a legitimate question because nobody at Celtic can claim the schedule has crept up on them. This club goes into every season knowing European football will be combined with league and cup games. There will be weeks when Celtic play every three or four days. That’s the job.

You can’t have players struggling to maintain the required intensity beyond an hour while simultaneously having such a significant drop-off when you replace them.

That’s the part that worries me.

If O’Neill had a deep squad packed with quality, tired legs could be replaced without Celtic losing much. If he doesn’t have that depth, he needs his strongest players capable of carrying the load.

Right now, I’m not convinced he has either.

Falkirk should have been put away. Instead, their goal changed the mood completely and Celtic found themselves hanging onto a game they had controlled.

Against Falkirk, they got away with it.

Against LASK, they didn’t.

That’s why Saturday can’t simply be filed away as a decent response and three points in the bag. Celtic have been given two warnings in the space of a few days, and one of them has already cost the club enormously.

O’Neill needs more from the players he has, particularly physically.

He also needs more quality to call upon when he turns around and looks at his bench.