Dundee United boss Jim Goodwin hailed a "remarkable effort" which saw his side produce a superb comeback to defeat Aberdeen, leapfrog them into fourth place in the Scottish Premiership and clinch European football.

After 55 minutes it was a scenario that looked unlikely, as United trailed to Jeppe Okkels' first-half strike as St Mirren held a shock lead at Celtic Park.

But Goodwin's side - having slowly turned the momentum of the game by peppering Aberdeen's box with crosses - completely changed the complexion of their season in seven second-half minutes.

Firstly, Glenn Middleton arrowed in a cross from a corner and Declan Gallagher planted a header into the net to level the game on his last appearance for the club.

Then, top-scorer Sam Dalby caressed in a penalty after Ryan Strain was tripped by Ante Palaversa.

That roused a previously forlorn Tannadice, which had been contemplating a sixth-place finish and the ceding of a nine-point lead to St Mirren in just five games.

"We feel absolutely brilliant, as you can imagine," said Goodwin after a dream first season back in the top flight.

"The celebrations in the dressing room are great to see. I just think it's a wonderful way to finish off a really good, strong campaign.

"It's been a remarkable effort from top to bottom at the club. It's been a really good two years."

Instead it is Aberdeen who end the season having lost huge leads over all of their nearest rivals to slide to fifth place.

Jimmy Thelin's side still have the opportunity to qualify for the Europa League play-off - and a guaranteed Conference League place - if they beat Celtic in next week's Scottish Cup final.

But the odds are stacked firmly against them in that game, so a start in the Conference League qualifiers seems more likely after their fifth-placed finish.

The sinking feeling for Aberdeen only got worse when substitute Jack MacKenzie left the field bleeding and bandaged up after being hit by a seat thrown from an area of the ground housing the travelling fans.

Goodwin said pre-match that going into the final game with a chance for fourth place was an achievement in itself, given United were only promoted this season.

He was right. But given they went into the split with a nine-point advantage over St Mirren which rapidly disappeared, it might not have felt like a successful season had they ended sixth.

As it happened they rediscovered what had made them an effective team in the Premiership at the crucial moment.

Goodwin has kept it simple. A solid structure and hard-working players with a big man up front in Dalby who has been lethal in the box when given quality service through Will Ferry, Strain, Middleton and others swinging in crosses.

When they turned to that after the first 30 minutes they got so much joy against a frail Aberdeen team and eventually their series of crosses paid dividends.

It has not been a thrilling recipe but Goodwin understands what it takes to be successful in the Premiership.

It is to his and United's credit that with a much-reduced budget and some significant injuries in a long season, they have finished as the league's fourth best side.

Fans may want more in attack next season but all of that can wait. They can enjoy the warm glow of a fruitful campaign.

If United end their league campaign with a glow, Aberdeen's has finished with deepening questions about Thelin's project.

It started in unbelievable fashion with 15 straight wins in all competitions and talk of a title race but since mid-November they have been the worst team in the league by points gathered. They have won five of their last 27 league matches.

While United, St Mirren and Hibernian have sorted the fundamental cornerstones of what makes a successful Premiership side, Aberdeen have not.

They are vulnerable defensively, particularly in dealing with balls into their box, and their lack of power and mobility in midfield is regularly exploited on the counter.

A goal difference of -13 is testament to that, as is the way United put them under pressure after a bright 30 minutes at Tannadice.

Thelin does not appear to have learned from this over the course of the campaign, since a 6-0 League Cup semi-final defeat by Celtic appeared to shatter their confidence in the autumn.

Winning the Scottish Cup next week against Celtic would be the salvation of all footballing salvations for the Aberdeen manager.

But either way, the club may need to think about whether their recruitment strategy and style of play is suitable for the unique rigours and pressures of Scottish football.

Dundee United manager Jim Goodwin: "We've been getting a lot of criticism, and rightly so, for our performances in the past four games.

"But the league is decided over 38 games not just the last four. We gave ourselves an opportunity today.

"I've had a couple of promotions as manager and enjoyed those moments. Today feels like one of those moments in qualifying for Europe.

"It will be a new experience but one we're excited for."

Aberdeen manager Jimmy Thelin: "In the end, our game summarises our season a little bit. It has been inconsistent in games and between games.

"It can be short moments in the games when we fall too deep and can't really control the situations.

"That's a thing we have identified and tried to work with and do better."