Among the notable progressions that have been made within the Celtic squad over the last ten days or so, the resurgence in form of certain players has been difficult to miss.

Ryan Christie has posted a reminder of what he offers when on song and in tune with those around him but, equally, Tom Rogic has reminded everyone about what he brings.

It is easy to forget given his longevity at Celtic that Rogic is still only 28 and with a fair bit of football left in him. The Australian midfielder had drifted out of the picture last season but the evidence of recent games is that the role Ange Postecoglou, his former Australian manager, has asked him to play is one he enjoys.

An elegant midfielder, it is not Rogic’s quality that has ever been in doubt but there have been perennial question marks over his match fitness and ability to last the course, which may seem unfair when stats and numbers are analysed over the long term.

In any case, Postecoglou has so far been able to coax out the kind of influential performances from Rogic in the middle of the park that bode well for the campaign that lies ahead. Given the high tempo, high energy way the Greek-Australian wants Celtic to play, it will be vital to have decent depth within the squad.

READ MORE: Celtic boss Ange Postecoglou's 'selective' transfer comments show he's now dictating business

In that regard for all that there has been an optimism surrounding recent performances there remains a need for reinforcements before the closure of the transfer window at the end of the month.

Defensively Celtic still carry a fragile look whenever there are questions asked in that area of the pitch, although Joe Hart’s double save on Thursday night against Jablonec got as big a roar as the three goals scored.

But while Celtic were able to coast past the Czech side, this week and this month as a whole offer bigger challenges.

The League Cup game today against Hearts will be a barometer in terms of how much Celtic have improved in a fortnight while the Europa League game against AZ Alkmaar will raise the bar considerably in terms of the tests that Postecoglou have faced so far.

The Dutch side have cashed in on a few players – Myron Boadu has gone to Monaco in a €17m move after the 15 goals he netted last term helped the club to a third-place finish – but they will offer Celtic a stern examination.

With a League Cup tie, a Europa League qualifiers and critical league games all coming in the next few weeks it is imperative that the recent sense of well-being is allowed to continue to take root.

The only way to do that is by keeping the results and the performances coming.