The striker came to the rescue to level Damon Gray's opener but could not find the goal that would snuff out the threat of the battling Irn-Bru First Division outfit.

It was the second cup shock in 24 hours after Celtic were dumped out by Aberdeen and both teams now have to do it all again in the replay at Firhill to earn the right to face St Johnstone in the semi-finals.

Rangers boss Walter Smith made six changes with Boyd rewarded for his Hampden heroics with a starting role and Charlie Adam, Steven Whittaker, Kevin Thomson, Steven Naismith and Nacho Novo also drafted into the team.

Barry Ferguson missed out with an ankle problem - the captain's armband was worn by Carlos Cuellar for the night - while David Weir, Sasa Papac, Brahim Hemdani, Chris Burke and Lee McCulloch were all rested following their CIS Insurance Cup final efforts.

Despite those changes, there should have been enough quality within the ranks to overcome a side sitting mid-table in the First Division without too much difficulty but Rangers had not reckoned on a plucky performance from Partick.

The best of the early chances did fall to Rangers but poor finishing seemed to be a problem for the front players. Novo was first to have a go when he collected a loose ball 25 yards out only to see the effort whistle past the post.

Boyd then threw himself in front of a Naismith cross but the man who saved Rangers on Sunday was uncharacteristically off-target as his header sailed inches over the crossbar.

At the other end, Simon Donnelly was wasteful with a free-kick just outside the box, before Scott Chaplain drilled a long-range shot wide of Allan McGregor's left-hand post.

Boosted by those half-chances, Partick grew in confidence and had an excellent opportunity to take a shock lead midway through the first half.

Mark Roberts found Gray in plenty of space but he was denied the opener by a timely save from McGregor who parried the well-struck shot to safety.

Rangers could have seized the initiative instead when Novo embarked on a decent run down the right flank, before delivering a cross into the box which broke to Adam but he drew groans from the Ibrox crowd by blasting well wide.

If that miss was poor, Steven Davis' was even worse. A Whittaker ball was collected by Naismith on the left and he teed up the shot perfectly for the Northern Irishman but woeful finishing let Davis down.

Kirk Broadfoot picked up the first booking of the game a couple of minutes after the restart for a challenge on Donnelly, before Donnelly earned himself a yellow card for dissent soon after.

Rangers piled forward in numbers in a bid to break down Partick's stubborn resolve and only the woodwork prevented Naismith from breaking the deadlock when his header from a Davis cross clipped the bar.

With almost an hour gone, Smith shuffled his pack and Adam was withdrawn for Burke. He wasted no time in embarking on a powerful run through the middle before setting up Novo out on the left flank but, again, the end product was lacking.

Ibrox was stunned into silence when Partick surged into the lead after 67 minutes. Gary Harkins slipped a great ball through to Gray who gleefully despatched past McGregor from inside the box.

The goal sparked wild celebrations among the vocal travelling support but Rangers were back on level terms just two minutes later as Boyd once again proved to be in the right place at the right time.

Thistle goalkeeper Jonathan Tuffey was forced to parry from one of his own defenders, sparking a goalmouth scramble with Boyd lurking to bundle home at the far post.

Partick then defied all the odds to hold on and earn the right to face the SPL leaders again on home territory in the replay.