CELTIC are not being kept awake at night by the thought of the Premiership challenge mounted by Aberdeen, but Ronny Deila yesterday had the unmistakable look of a man who hadn't had much sleep.

On the flight back from Milan he watched a recording of Celtic's victory over Hamilton last weekend, and as usual his mind then continued to whir into the early hours after arriving back in Glasgow. Deila is like the team he has fashioned - young and energetic - but taking on Inter Milan in the San Siro asked a lot of Celtic on Thursday night. It will be fascinating to see their physical readiness for an Aberdeen team which is just as fast and fit.

It was a credit to the team sitting second in the league that there wasn't much of a Europa League post-mortem during Deila's press briefing at Lennoxtown. Aberdeen at Parkhead has returned as a fixture demanding respect and a line of questioning of its own. Celtic are three points clear at the top of the Premiership with one game in hand (and a goal difference advantage of 13). A home win would snuff out any real prospect of Aberdeen hanging in there. Derek McInnes's side is without the influential Jonny Hayes but their recent performances have been impressive, they are fresh and rested, and they will sense that they might capitalise on a physical advantage over Celtic after Milan. It is only 12 months since they came to Parkhead and delivered a big win in last season's Scottish Cup fifth round.

Aberdeen's current run of 13 games unbeaten is the longest by any team in the Premiership this season. The last side to beat them in the top flight was Celtic, a result which did much for the bond between Deila and his supporters. That day saw the first of the post-match fist pumps which have become routine. He knew the significance of that outcome at Pittodrie on November 9 - it took Celtic top of the league for the first time since he took over - and he is equally aware of the context this time.

"I don't think it's a cup final for us, I think it's a cup final for Aberdeen. But we want to win and we know what's in it if we win. We can be nine points ahead of them - with the goal difference as well - and then it's going to be tough to reach us and take us back. The league is the most important thing. The only thing I was thinking when I was finished with the Inter Milan game was 'I want more of this, I want to play these games at this level'. If we want that, Sunday is the time to show that we want it. The league isn't over if we win but we would have put ourselves in a very, very good situation."

There was a 5-2 Celtic win at the end of last season but four of the last five meetings between the clubs have finished 2-1, Celtic winning two of those and Aberdeen the other two. Deila recognises qualities in Aberdeen that are absent in the other domestic challengers. "This is a big game. It's easier to meet Aberdeen than to meet - no offence - St Mirren or Motherwell because we know we have to be really up there to beat them. I think they are a good team. They are very clear, you can see the pattern all the time, what they are doing. They are very good on the counter-attack. And they have consistency in their squad and in their management and then they get improvement from that. That's what we want as well. They don't have anything else to play for and they strengthened their team in January as well, so of course they are wanting to win the league."

That flight back from Italy touched down shortly before 1.45am on Friday, and tomorrow's kick-off is at noon. Was that a concern for Celtic? "We're going to be ready for the game." Leigh Griffiths is unlikely to be ready after requiring a protective boot on his ankle having been accidentally stamped on during a training session. His unwitting assailant was Nir Bitton, so it counted as almost the only foot the Israeli has put wrong in recent performances (although he allowed Fredy Guarin too much room to collect the ball and hit his terrific late winner for Inter).

Tall, thin, and languid, Bitton looked ill-equipped for the frenetic battles of Scottish football at first and was not an initial Deila favourite. But they talked, he toughened up, and he has recently emerged as a figure of poise and influence in central midfield. "I couldn't see how we were going to use him if he didn't get more intensity in what he did, and that starts in training," said Deila. "We had a very good talk and he has really, really put the effort in that he needed. You can see what he gets out of his talent now and this is just the start."

Lunchtime kick-offs often have a deadening effect on matches and Celtic can be forgiven if sluggishness shows in their play, but a crowd of around 50,000 is expected and that is high for a domestic fixture. For the Premiership to have something close to a title race at the start of March is an attractive novelty. To keep it alive, Aberdeen must avoid defeat.