A late strike from substitute Scott Fraser sealed Dundee United's place in the William Hill Scottish Cup quarter-final at the expense of Partick at Tannadice.

Mixu Paatelainen's bottom-of-the-table side received a welcome break from the pressures of the Ladbrokes Premiership thanks to Fraser's well-taken 85th minute goal just when it looked liked this fifth round tie was heading for a replay at Firhill on Tuesday night.

This was a typically tough cup tie but United ultimately edged out Alan Archibald's visitors to take their place in the last eight.

These two teams were meant to meet the week earlier in league business, only for the Firhill pitch to be ruled unplayable.

Still, Partick arrived on Tayside buoyed by Tuesday night's 1-0 Premiership win over Motherwell thanks to Steven Lawless' last-minute goal.

They started well and in the ninth minutes Sean Welsh's 22-yard shot was spilled by home goalkeeper Eiji Kawashima before the United defence hooked the ball to safety at the expense of a corner.

United were finding it hard to get going although nine minutes later midfielder John Rankin forced his way into the box, but saw his shot deflected wide by Thistle's Frederic Frans.

The visitors looked the likelier side to make the breakthrough.

Towards the half-hour mark, Callum Booth's cross from the left was aimed for Lawless, but he could not get the ball at the far post after Kawashima had come off his line trying to smother.

At the other end, the hosts finally put together a flowing moved when Guy Demel fed Billy McKay who, in turn, released Simon Murray who tried to angle his shot across the body of Tomas Cerny, but the visiting keeper held it well.

The second half started with Demel linking with Blair Spittal before Paul Paton shot high over the bar from 25 yards.

Thistle made a double substitution in the 64th minute in a bid to win the tie as Mathias Pogba and Gary Fraser replaced Welsh and Kris Doolan.

United almost opened the scoring in 67 minutes. Rankin went on a surging run down the left before crossing low into the six-yard area where Murray was lurking - it looked like he would put the hosts in front but the striker just missed out.

In the 76th minute United substitute Scott Fraser almost made an instant impact as he hit a goalbound shot, only for it to be deflected wide by Welsh.

But the youngster was not to be denied with five minutes left as he latched onto Spittal's pass and steadied himself before slotting a left-foot shot into Cerny's far post for the winner.