When Celtic came to McDiarmid Park last season, Brendan Rodgers said he had “never been so angry at half-time” as a manager as his side trailed before going on to win 3-1.

On his second pilgrimage to Perth since returning to the club, Celtic put in a hugely impressive first 45 minutes and netted three terrific goals.

This time around, he said his half-time mood “was a bit different”.

But why are so many things about this Celtic side different to last season? According to Rodgers, Celtic “weren’t on the same page at that point in time”.

In total, six goals were scored by Celtic in Perth and it was a scoreline that flattered St Johnstone.

The visitors had 19 shots at goal, 11 on target. They entered the final third 98 times and had 38 touches in the box. In comparison, Saints had nine.

There’s a ruthlessness and a relentless about this side that leaves the rest of Scottish football with much to ponder this season.

But an acid test lies in wait for Celtic against Borussia Dortmund on Tuesday. Rodgers said “preparations start tonight” for their second Champions League game.

The coming week’s jaunt to Germany has long been on the mind of many supporters, but pre-match Rodgers stressed his sole focus was on St Johnstone, though he wanted “a Champions League level performance”.

After Daizen Maeda’s volley was chalked off, Kyogo Furuhashi took two touches to cushion in the opener. Paulo Bernardo bookended an excellent team goal before Kyogo cutely cushioned in the third.

That tally was matched in the second half. From Callum McGregor’s piledriver, to Maeda’s neat nod and Adam Idah’s finish following a silky move, the Scottish champions were on another level.

Under Rodgers’ predecessor Ange Postecoglou, Celtic once hit Dundee United for nine. They never quite reached double figures in Perth but they could have.

“This is as good a football team I’ve seen in Scotland for years,” former St Johnstone player Allan Preston said on BBC Radio Scotland’s Sportsound.

“I don’t know the last time I saw someone as fluent, as crisp as that. I honestly think they are better than Celtic were under Ange Postecoglou.”

Though that first half showing back in December left Rodgers at his angriest, his side still scooped up three points in a 3-1 win. But they were not gathered the way he wanted them.

There was not the dominance and desire there is now. Nor the hunger and hunting, which is continuing to be led by Maeda.

The Japan international, who Rodgers said just over a week ago was better than anyone at tracking back defenders, was at it once more at McDiarmid.

Six goals up and 86 minutes on the clock, he charged back and robbed David Keltjens in Celtic’s half. He leaves you exhausted merely watching on.

Fleetingly does the Celtic manager single out a player, but he did so again with Maeda, and indeed the goal he had chalked off, which he believes was the wrong call.

But as his work-rate typifies that of the mentality monsters, his own projection in performance aligns with what Rodgers has rallied for.

The one thing missing in Maeda’s game had long been goals. The energy, the enthusiasm and exceptional pace was evident, but goals evaded him.

In Perth he picked up another, and perhaps should have had one more. In total last season, he only scored six in the Scottish Premiership.

“He is getting the reward for all that work by scoring consistently,” Rodgers said. “It’s maybe something he could have been better at but he’s getting into good positions now.”

It’s not just Maeda in a good position, Celtic couldn’t be better placed to take on Borussia Dortmund.

All this was done today with Reo Hatate, James Forrest and Idah sitting on the bench for 66 minutes.

Cameron Carter-Vickers was out injured, while Luis Palma was absent from the matchday squad too.

Even without such players, Rodgers saw everything he could have wanted to see. The rest of Scottish football are shutting their eyes.