Celtic have seemingly only gone from strength to strength during Ange Postecoglou's tenure thus far, although the Hoops were brought crashing back down to earth on Sunday afternoon, following a dismal 2-0 defeat away at St Mirren.

After an initial slow start to life in the dugout at Parkhead, the 57-year-old has since sparked a real turnaround in fortunes over the past 12 months, having overseen a stunning 38-game unbeaten in the Scottish Premiership.

Almost exactly a year on from their last league loss away to Livingston, that remarkable streak came to an end yesterday in Paisley, with goals from Mark O'Hara and Jonah Ayunga powering Stephen Robinson's side to a deserved victory.

With it seemingly having been plain sailing in the early weeks of the season for the Old Firm outfit domestically, alarm bells will seemingly be ringing for Postecoglou following that limp display, as his much-changed side struggled to contend with their spirited hosts.

In the aftermath of that loss, the former Yokohama boss accepted responsibility for the performance as a result of his team selection, admitting that he potentially got it "wrong" after making six changes from the side that drew with Shakhtar Donetsk in the Champions League in midweek.

The Greek-Aussie had only recently lauded the strength in depth at his disposal following an impressive window that saw nine major deals completed, although there may well now be concern over the quality of those in reserve as the few handed a rare chance to impress failed to deliver.

Summer arrival Aaron Mooy was one who notably underwhelmed on what was his first league start for the club, having come under fire from club legend Stylian Petrov for failing to track his runner in the build-up to O'Hara's opener.

Academy graduate Stephen Welsh was another who was unable to take his chance after replacing the injured Cameron Carter-Vickers in the backline, with the defensive unit as a whole having been simply "bullied" by opposition striker, Curtis Main.

While Postecoglou suggested there was no obvious villain on the day as the collective performance was simply lacking, he may well have his eye on a few disappointing stars who have subsequently failed to warrant a more prominent role.

Such a woeful outing should well serve as a warning to the Hoops boss moving forward that he may not be able to rotate his squad quite as freely as he may have hoped, with the Buddies proving to the champions that they won't get any easy ride in the defence of their title.