PROGRESS can sometimes be measured in intangibles which is maybe just as well for Ronny Deila and Celtic. For the numbers relating to his side’s defensive record in Europe do not suggest they are moving in the right direction. In 11 Europa League matches since Deila succeeded Neil Lennon in the summer of 2014, Celtic have kept just one clean sheet. They have not won any of their last eight games in that competition, conceding 18 goals in the progress. On the plus side they have developed a useful knack of scoring in Europe – only in the San Siro have they failed to find the net in those 11 matches – only for those goals to be cancelled out by the sheer volume being rattled past goalkeeper Craig Gordon at the other end. It is that defensive inefficiency that is proving so costly to Celtic’s European ambitions although an obvious fix is not so easy to pinpoint.

The lunchtime after the loss in Molde, Deila looked like a man carrying the weight of the world on his shoulders. In mitigation, his appointment with the Sunday journalists was his third press conference in quick succession and, on top of the early morning arrival back home from Norway and dealing with the Kris Commons commotion, this was probably the last thing he needed. Proper analysis of his team’s performances would be best shared with his backroom team and his players, not a room of reporters, and for once the usually loquacious Deila was not of a mind to be particularly expansive. But one snippet, in his idiosyncratic English, was particularly revealing: “I think some of the mistakes are having a pattern.”

This much is true. Celtic continue to leak soft goals in Europe, either from individual lapses in concentration, from set-plays, or, as was the case the other night, from being caught too far up the field and being sprung on the counter attack. That it keeps happening is a source of huge irritation to Deila who now has 11 days to alight on a solution before Molde come to Glasgow for the second match of the double-header. A similar defensive performance will surely only deliver a similar result for Celtic.

“We need to find the balance between attacking and defending,” he added. “Some games we’ve done that well, some not so well. That’s something we have to learn from individually and as a team. I think consistency is important in the back four and we have changed a lot and that has hurt a lot. If we can play a consistent back four then we will get safety and have better relations.”

Deila spoke forlornly about the loss of Virgil van Dijk and Jason Denayer from last season’s team, although nostalgia can often play tricks with the mind. In eight Europa League games last year, Celtic were far from the rock-solid defensive unit that many now seem to be wistfully recalling, keeping just one clean sheet in that time.

There was, at least, little doubt who his first-choice central defensive pairing was. This season, due to injuries and other factors, it is hard to say with any authority who the automatic picks would be were everyone available, with Efe Ambrose, Dedryck Boyata, Jozo Simunovic, Tyler Blackett, Eoghan O'Connell and Charlie Mulgrew all having filled that role at one point this season. Deila would not confirm that Simunovic and Boyata were his first-choice, although given those were the pair the club lavished transfer fees on during the summer, it is probably fair to assume that to be the case. The Norwegian did acknowledge, however, that keeping players fit and allowing them to forge a better understanding would be pivotal in improving Celtic’s defensive record.

“We will see [who the best back four is],” he said. “We have a lot competition but we have our thoughts. I have a picture in my head of course. We have had some injuries in the back four and that has made it more difficult.

“Having a partnership is very important. You need consistency. We lost Virgil who was an important player for us. After that I brought in two players. Jozo has been out for a while. Tyler is a young player coming up who we have had for a few weeks now and that is a positive.”

There will be pressure on Simunovic to succeed with Celtic having splurged somewhere in the region of £5.5m to sign him from Dynamo Zagreb. Injuries have prevented him having a sustained run in the team, and Deila urged against expecting too much, too soon from the 21 year-old.

“Things take time. It is not like buying someone, just put him in and everything is perfect. He needs time to get to his best level. First of all he has to be injury-free. But if you are a quick learner and have the ability we know he has, then you can improve very quickly. It is about quality, playing together over time, talking together and making improvements. We lost both centre halves from last year and it takes a bit of time to replace them especially if we have players unavailable.”

Celtic will look to this afternoon’s visit of Dundee United as a chance to atone for the mess in Molde, a team whose form has nosedived since the sale of Stuart Armstrong and Gary Mackay-Steven in the January window.

“I’m quite surprised [to see United at the bottom of the SPFL Premiership],” said Mackay-Steven. “I know a lot of the boys and they’re better than the table shows.”