ST Johnstone's annual big win at Parkhead.

It says something for the results Tommy Wright and his players can pull off that throwing a spanner in Celtic's works last night didn't even count as their most memorable result in this stadium in the past ten months. They won the Scottish Cup here last May and now they've thrown a cat among the pigeons by bringing Celtic down again too, just as they did in 2011.

Danny Swanson felt ill on the morning of the game but slid out of his sick bed to smack home the goal of his career, a screamer past Craig Gordon. Celtic looked leggy, lacking zip, and St Johstone's calm, intelligent and bold play saw them across the line for a result which lifted them into the top half of the Premiership. In the previous 11 domestic games Celtic had kept 10 clean sheets. The only side to find a way through them? St Johnstone. Celtic's efforts came to a peak against Inter Milan and Aberdeen and three games in seven days caught up with them. But this was a St Johnstone win more than a Celtic defeat.

"We asked them to be brave in possession and they were," said manager Tommy Wright. "When you come here you have to try to keep the ball and we did that. That gave us the platform to go and win it. And we got a great goal. I can't remember many clear-cut chances for Celtic. Nobody can say that overall we didn't deserve the victory. If we finish in the top six again it would be a magnificent achievement. For a club our size to be in the top six four years running is a tremendous achievement. We haven't achieved it yet but that's our aim."

Celtic might have gone nine points clear at the top. Instead the lead remains at six and manager Ronny Deila was subdued.

"It's not good to find excuses. The performance was not good enough. But it has been a very, very hard programme for us. We have played big, big matches and today we got a big setback. We have to bounce back on Sunday [against Dundee United in the Scottish Cup]. Every time we play in Scotland we are favourites and we should win. Today we had a lack of fight. In the end we got too open and didn't press as a team.

"Offensively we got into the centre all the time, we need more width and crosses and not be so easy to read. There wasn't that determination that they really wanted to get that ball into the net."

Deila had tweaked his team. Stefan Johansen dropped back alongside Scott Brown at the base of the midfield and Stuart Armstrong got a turn playing in the hole behind the centre forward, with Gary Mackay-Steven to his right and Anthony Stokes left. Armstrong was always a mobile footballer but it's impossible to look at him at the moment without marvelling at the amount of ground he covers.

That's what Deila asks of his players and the new pair are delivering in spades. St Johnstone did well to hang in as Celtic flew at them through the former Dundee United men and Griffiths. Armstrong had one effort blocked by Dave Mackay and another parried away by Alan Mannus. The goalkeeper was just as sharp in pushing away a stylish Mackay-Steven shot to the top corner. Celtic loudly claimed for a penalty when Virgil van Dijk's shot hit Steven Anderson's arm.

All of this pace and movement didn't last. St Johnstone were under pressure, but never under a bombardment. They had shape and structure and continually make the interceptions which frustrated Celtic and allowed them to take a breather. They were positive, too, playing David Wotherspoon up with Steven MacLean - how many visitors go two up front at Parkhead - and supporting them with willing runners from midfield.

Both of the forwards had half-chances before St Johnstone had their best spell of the night, the opening ten minutes of the second half which yielded their goal. They forced a corner and van Dijk seemed to have cleared the danger but his header came to Swanson. What a moment he delivered, unloading a stunning shot into the top corner of Gordon's net from nearly 30 yards out.

They'd have had a second from another corner a few minutes later if Anderson hadn't put his low shot past the post. From another corner, at the same back post, at the same end of Parkhead, he'd scored in the Scottish Cup final. Celtic responded, applying sustained pressure for the first time. They swarmed over St Johnstone. But their finishing was poor, usually too straight at Mannus. The more rushed they got, the more their passing let them down. And they lost Adam Matthews to a twisted ankle then put on Nir Bitton and James Forrest, to no effect.

Wright's boys - always calm, always intent on playing their way out of tight spots - never really looked in serious trouble. The only benefit for Deila was that his arm got a rest at full-time.

For once, no fist pumps or "Ronnie Roars" from him.