IT was the moment they had been waiting for. With 66 minutes on the clock at Tannadice yesterday, the fourth official’s board went up and the away fans heartily welcomed Scott Allan into the fray for his first competitive action as a Celtic player.

His outing included a couple of trademark defence-splitting passes, plenty of tracking back and a booking for a foul on Aidan Connolly, but in general this was a cameo rather than a leading role.

In a match where Ronny Deila could make nine changes from the midweek starting line-up and still leave Allan on the bench, it was also a glimpse of the work he must do if he is to be more than just a member of the supporting cast.

Kris Commons, just one of Allan’s potential rivals for a first-team place, was omitted from the action in the first leg of the Champions League play-off against Malmo on Wednesday night but ended the day with the captain’s armband and could quite easily have scored a hat-trick here.

Just for good measure, there was chat about a loan move for Ryan Gauld of Sporting Lisbon overnight, but sources close to the club were pouring scorn on that idea yesterday.

Allan said after the final whistle: “I got a great reception from the fans, it was different class. Kris Commons came into the starting line-up and he was great. He’s been one of Celtic’s main performers for years now and I’d like to think I could become like him in the future by looking at what he’s been doing. But there are a few in the squad I can learn from, to be fair.”

Celtic and their fans have learned to loathe these pesky Premiership matches which just happen to be sandwiched between crucial £16 million Champions League showdowns. Twelve months ago the Scottish champions made 10 changes in the midst of an angst-filled play-off tie against Maribor and lost 1-0 to Inverness.

Once again, the Celtic manager placed a premium on protecting legs ahead of Tuesday’s second leg, his changes including the competitive debut of goalkeeper Logan Bailly and a surprise recall for Anthony Stokes.

Dundee United are currently a team with no shortage of troubles. A section of the Tannadice support chanted against manager Jackie McNamara following last week’s 4-0 defeat at Hamilton, doing little to dampen rumours of boardroom unrest which have coalesced around the recent suspension of respected youth coach Stevie Campbell.

The hosts badly needed a win but you wouldn’t have guessed it from the way they started. Instead it was Celtic who came out of the blocks the faster, with much of the running being made by the two men who did feature against Malmo, Emilio Izaguirre and Leigh Griffiths.

The striker headed over within two minutes while the Honduran’s bursts down the left were driving United to despair.

When an Izaguirre pass left Mark Durnan unsure whether to play offside after 17 minutes, Griffiths skipped round United goalkeeper Luis Zwick and rolled the ball into the net from an angle. He celebrated it with a thumbs up to his detractors behind the goal.

With Celtic exerting a worrying dominance on their hosts, former Queen of the South defender Durnan had already cleared a Commons effort up and off his own bar early on, while Zwick waged a one-man campaign to keep Commons off the scoresheet.

Further goals were long overdue before two arrived in a minute on the stroke of half-time.

First, Durnan comically walked the ball into his own net in a vain attempt to prevent a Commons square pass reaching Griffiths in the area, then United finally produced some quality.

The home side’s only attacking ventures worthy of note had produced a clumsy challenge from Bailly on Robbie Muirhead on the edge of the box which might have presented them with a penalty, and a wasteful Ryan McGowan finish after a neat four-man move.

However, they reduced the interval deficit to a single goal after young Scott Fraser wriggled past a couple of players and tempted Efe Ambrose to send him crashing to the turf, with Chris Erskine sliding the penalty home.

The clinching goal after 74 minutes came from Celtic substitute Callum McGregor. His strike deflected off Coll Donaldson and ended up in the bottom corner following lead-up work from Stokes and Gary Mackay-Steven.

McNamara said: “It has been transitional for two-and-a-half years here but the team is young, we have players to come back who are going to strengthen us. I am not going to panic.”