St Mirren followed up midweek European progress by inflicting an opening Scottish Premiership defeat that was labelled "unacceptable" by Hibernian head coach David Gray.

In a full-blooded encounter, three second-half goals - one from Roland Idowu and two in quick succession from substitute Oisin Smyth - comfortably downed the visitors in Paisley.

Hibs, playing under Gray's permanent stewardship for the first time in the league, started well but St Mirren motored away after half-time.

It could have been very different had Hibs striker Dylan Vente buried his first-half chance, missing from three yards out, but it ended up foreshadowing an ugly afternoon for the Leith side.

"The performance is irrelevant when you lose the game 3-0," Gray told BBC Scotland. "I can't accept that, we can't accept that moving forward.

"In the first half we had enough chances to go in front. We don't take them. It's been a theme for a wee while. The goal we lose starts with three or four mistakes and we can never accept that.

"It's nowhere near where we need to be. The standards have been set from day one. We know in both boxes we weren't good enough again today and that's a concern.

These two met on the opening day of last season but fortunes have changed significantly since then with St Mirren starting the year in European qualification and Hibs bedding in yet another new manager.

The visitors started the brighter and should have been 1-0 ahead after eight minutes. Jordan Obita whipped a brilliant ball in from the left and it bounced awkwardly to the back post, where Vente somehow chipped into the air instead of tapping in, allowing Alex Gogic to block on the line.

St Mirren, buoyed by the midweek win over Valur, took the lead just after half-time through Idowu. Running on to a Jaden Brown through ball, he cut back on to his right, dismissing Nathan Moriah-Welsh, and thundered a shot into the far corner.

The Irishman almost had a second when the ball broke kindly to him in the Hibs box. Cutting back on his left foot, he curled a shot on to the face of the post that was blazed over on the rebound.

Substitute Smyth was responsible for the second and third, with James Scott assisting both. The former Hibs striker picked off a loose back to chip the ball back to Smyth, who placed his header into the corner.

The killer blow came less than two minutes later. Scott burst down the right, sliding the ball inside to Smyth who slotted perfectly past Joe Bursik.

Although there might be debate about the quality of St Mirren’s Europa Conference League opposition last week - some compared Icelandic side Valur to a Championship team - you can only play what is in front of you and the Buddies dispatched Hibs with similar ease.

The first half was rough and tumble, and the hosts only really created something when they countered.

Once they had absorbed that early pressure, they kicked into life. Driven forward by Idowu in midfield, they became more clinical in the second half and a quickfire double wrapped up all three points.

All this was done without talismanic captain Mark O'Hara, who picked up a niggle against Valur. Despite the impressive performances throughout the team, Stephen Robinson will want him back sooner rather than later.

The first 10 minutes would have encouraged the travelling Hibs fans, but it soon became a story they have seen many times before.

Looking lively through Martin Boyle, 18-year-old Rudi Molotnikov and the rampaging Lewis Miller, a few missed chances saw the heads go down and the visitors retreated deeper and deeper.

The second St Mirren goal came from a defensive mistake, Marvin Ekpiteta the guilty party, and it became a truly familiar afternoon. The third soon followed and the promising opening stage was a distant memory.

Gray has a lot of credit in the bank. He is a local hero, the man who gave Hibs fans their best day, but if performances don't improve from the Nick Montgomery era, he will see his stock dwindle quickly.

St Mirren manager Stephen Robinson: "The first goal is always important and then we settled, we were in total control after that. When we were 3-0 up, we managed the game which is a big improvement."

Hibernian head coach David Gray: "We huffed and puffed at times and had a few half-chances but the damage had been done at that point."