Marcus Fraser's own goal and Amar Fatah's emphatic penalty gave Dundee United a vital three points from a hard-fought Scottish Premiership encounter with St Mirren.

The hosts' first win in four games keeps their faint hopes of a top-six place alive and is a huge boost to Jim Goodwin's side before their Scottish Cup quarter-final against Falkirk.

Goodwin admitted he had one eye on the chance to reach Hampden even as his side prepared for the visit of Stephen Robinson's team, and he was delighted to be heading to be turning his full attention to the knockout competition in a winning mood.

"We didn't want to go into the Falkirk cup game off the back of two defeats," the United manager said. "Tonight's game is done, the whole focus now is the game on Friday."

United had the perfect start, taking the lead after just eight minutes, but they had St Mirren's Fraser to thank.

Vicko Sevelj's powerful shot was well saved by goalkeeper Shamal George, but instead of heading the ball out for a corner, the visiting centre-half inexplicably nodded into his own net.

St Mirren have had a poor record after falling behind this season but grew into the game and had two good chances to level in the first half.

Dan Nlundulu forced a save from a narrow angle and then Mark O'Hara put a shot left of the goal when he had a chance to really test goalkeeper Ashley Maynard-Brewer.

United had the last chance of a competitive first half when Panutche Camara forced George into a save but had to settle for a single-goal advantage at the break.

St Mirren manager Stephen Robinson made a switch at half-time, bringing Jake Young on for Roland Idowu - and he got an immediate reward.

A free-kick on the left allowed Scott Tanser to deliver into the box and, when the ball dropped to the striker, he sliced a shot into the top corner to level the score.

United responded well, but St Mirren went close to taking the lead when midfielder Killian Phillips crashed a header off the woodwork just after the hour mark.

The hosts took the lead from the penalty after a bizarre incident.

As Alex Gogic raised his arm to claim for offside as free-kick was curled into the St Mirren box, it connected with the ball following Ross Graham's flick-on.

After a lengthy video assistant referee check, Fatah stepped up and rifled his penalty past George.

The goal was soon followed by another huge roar from the United support as former Scotland forward Johnny Russell came on for his second debut after rejoining the club earlier in the day.

The Tannadice favourite could not help his side find a third goal to take the nerves out of the finale, but United held firm through six added minutes for a morale-boosting victory.

With less than 10 minutes to go at Tannadice, United looked destined for yet another of the draws that have cost them success this season.

On numerous occasions, United have taken the lead in Premiership games only to come away with a point when they could have had three.

And Goodwin has bemoaned the fact that those lapses had a huge effect on their league position.

Fatah's penalty changed the narrative and Goodwin and his players can now look forward with optimism.

The gap to sixth-placed Falkirk is down to nine points with three to play before the split, probably insurmountable but still possible.

However, it is a massive shot in the arm before facing John McGlynn's side in the Scottish Cup on Friday.

Reaching Hampden would put a different complexion on what has been a difficult season, and going into a huge match on the back of a hard-earned win will have lifted the mood after some dismal days in recent weeks.

Seeing Russell back in a tangerine jersey is the icing on the cake.

St Mirren manager Robinson had predicted an ugly game on a difficult surface but would not have been prepared for two horrific moments that cost his side.

Robinson might take encouragement from his side looking better with their familiar midfield trio of O'Hara, Baccus and Phillips starting again, but with his side just three points ahead of Kilmarnock and the play-off place, relegation fears are getting very real.

The League Cup winners have a Scottish Cup date to look forward to on Sunday, but Premiership problems will prey on their minds after another defeat on the road.

Dundee United boss Jim Goodwin: "We're delighted to win the game, really pleased with the physicality the players showed.

"We set the team up in a way where we had to compete and win our individual duels.

"The back three were really good at times, winning first contacts. The midfield three in particular were outstanding. I felt before the game whoever won the midfield battle would come out on top in the game."

St Mirren manager Stephen Robinson: "It's a poor game of football because of the pitch.

"We knew what we were coming into and they played it better than us at the start of the game. We told the players, but they kept trying to pass the ball on a pitch you just can't pass on.

"The two goals are the story of our season. I think anything that could go wrong has gone wrong."

It is a quick turnaround for United, who travel to face Falkirk in the Scottish Cup quarter-final on Friday (19:45 GMT).

St Mirren are back in action on Sunday when they host Partick Thistle in their own last-eight tie (19:30).

Both games are being broadcast live on the BBC Scotland channel.