St Johnstone hoped new signing Sammy Youssouf would answer their prayers - but the Scottish Premier League's bottom club now need miracles to survive relegation after this crushing home defeat.

Youssouf did head a late goal on his debut, but Dundee United star Derek Lilley stole the show with a glorious hat-trick with Charlie Miller also hitting the net.

The Saints' biggest sin this season has been their failure to hit the net and Billy Stark attempted to resolve the problem by signing the Dane from Hvidovre until the end of the season.

Youssouf certainly brought some rare glimpses of hope, but with Hibernian still 10 points clear and with a game in hand the doomed Perth side already look condemned to the First Division.

United looked on a high after their win over city rivals Dundee and they were unfortunate not to make a dream start inside the first three minutes as St Johnstone took time to get going.

Lilley exchanged passes with Jamie McCunnie outside the area before sending in a right-footed shot which Darren Dods managed to deflect wide of Alan Miller's post.

From the resulting corner Miller's cross was flicked on goalward by David Hannah, but Paul Hartley was stood on the goal-line to make the clearance.

St Johnstone seemed to grow in confidence from those misses opportunities and Youssouf led their pursuit of the opener.

Stephen Wright's error allowed him to get a shot on target which keeper Paul Gallacher did well to block and Craig Easton managed to get back to divert Hartley's follow-up effort wide.

The Dane almost got on the end of Hartley's cross in the 14th minute, but McCunnie made a vital interception to frustrate him.

United again breathed a sigh of relief in the 19th minute as Youssouf reacted quickest in the box from Graeme Jones' chip back from the byline, but his acrobatic overhead kick flew wide.

The Saints continued to struggle in front of goal and in the 25th minute Hartley should have done better.

He was freed by Jones and despite doing all the hard work to outpace McCunnie and Lauchlan he drove just over the ball.

And as so often has happened this season to St Johnstone, they paid the price for squandering those chances as the visitors took an undeserved lead three minutes later.

Steven Thompson flicked on Jim McIntyre's long ball and Lilley beat the offside trap to take the ball in his stride before hitting a low right-footed shot past Miller.

Youssouf was clearly St Johnstone's brightest hope and he went agonisingly close to levelling the scores just five minutes later.

He outstripped Hannah and Jim Lauchlan for pace, but he drilled his low right-footed shot just past the upright.

That visibly sucked the life out of the home players and they went a further goal down in the 36th minute.

Thompson broke free and pulled the ball back from the byline for Miller to comfortably side-foot home from 15 yards out.

It was inevitable that United would score, but they did so just before Stark could get about resurrected his side in the dressing room at half-time.

Miller burst through the midfield and Lilley ran onto his pass to force the ball past the onrushing Miller and the ball trickled over the St Johnstone goal-line.

The Saints were dead and buried, but Lilley was revelling in the spotlight and he notched his hat-trick in the 51st minute.

Miller teed him up from a free-kick and the United striker's 25-yard rocket flew into the corner of the Saints net.

The home players themselves seemed to concede that the SFL was beckoning as Easton struck McIntrye's cross against the bar.

Youssouf, however, got the goal his performance deserved in the 65th minute by heading Hartley's free-kick powerfully home and that seemed to lift the home side a little.

The impressive Danish marksman again went close a minute later as Gallacher saved his fierce right-footed shot and Hartley's follow up was cleared off the line by Wright.

Thompson went about restoring United's four-goal advantage in the 68th minute, but his curling effort went just past Miller's upright before the keeper denied him again with a good stop.

The travelling United supporters gave the substituted Lilley a standing ovation near full-time and promptly asked the delighted striker to give them a wave from the dugout.

That strangely did not materialise - but it now looks inevitable that St Johnstone will be waving goodbye to the SPL in May.

Teams

St Johnstone: Miller, Dods, McCluskey, Falconer (Russell 84), Lynch (Maher 77), Murray, Kane, Hartley, McClune, Jones (Parker 56), Youssouf.

Subs Not Used: Cuthbert, Connolly.

Booked: Hartley.

Goals: Youssouf 65.

Dundee Utd: Gallacher, McCunnie, Wright, Lauchlan, Hannah, Easton, Miller, Fullarton, McIntyre (Venetis 86), Thompson (Winters 90), Lilley (McConalogue 82).

Subs Not Used: Combe, McCracken.

Booked: McIntyre, Miller.

Goals: Lilley 29, Miller 37, Lilley 45, 52.

Att: 3,711

Ref: J Underhill (Scotland).