When extra-time was required last night after Rangers squandered a winning position, there were questions over their mettle - especially when Kris Doolan’s equaliser was rifled into the net with seconds of normal time remaining.
However, within eight minutes of the restart, Caixinha’s men had removed any doubt about the outcome in blistering fashion.
They did so thanks to two Caixinha summer signings coming to the fore when their team need them: Daniel Candeias lashing a powerful low effort past Ryan Scully from the edge of the box in the 93rd minute before the keeper was beaten when a cute back-flick from substitute Eduardo Herrera crossed the line with the help of a slight deflection.
Earlier, Carlos Pena - the midfielder who has been something of a mystery man since his apparent £2.7m move from Mexico in the summer - looked like proving the matchwinner with a deft backwards header from a Candeias corner after 57 minutes.
Rangers were their usual mix of the decent and the indifferent, meaning there was nothing in their play to suggest that they will provide a stiff challenge to Celtic when the two teams meet on Saturday for their first clash of the season. It might not help that experienced centre-back Bruno Alves was withdrawn with what appeared a knock.
The pre-match fixation with what the outcome could mean for Caixinha’s employment prospects in Scotland, and his contention that teams are more aggressive against his side than other “top teams” in the country, obscured to what else was on the line.
A total of 20 major trophies have been contested since one last resided at Ibrox. With Celtic’s strength putting the title out of bounds, cups are the only possibility of ended a silverware starvation that runs to six years. A time in which eight clubs with much smaller budgets than the Ibrox club have been trophy winners.
Last night’s quarter-final would once have been a guarantee of Rangers booking another Hampden outing. Partick Thistle haven’t reach the last four of a national cup since they were beaten 3-0 by Rangers in the Scottish Cup at that stage 2002. At 39, Alan Archibald is too young to have played the last time his team defeated Rangers, which was in 1993.
However, with the latest evidence of the flakiness that stalks Caixinha’s men coming at Firhill only on Friday, there weren’t many making confident predictions about what would happen when the teams meet at the venue for a second time in five days.
The straight red card shown to Chris Erskine was a break for Rangers that they could not fully capitalise on in being held to a 2-2 draw. A result that left them without a victory this season against any side that finished in the top six of the Premiership in the last campaign.
Early on last night they looked like putting that stat to bed as they dominated against a Thistle team that again operated with a back five. Constantly forced onto the back foot, the hosts should have taken the lead midway through the first period when keeper Scully clumsily beat out a shot from Alfredo Morelos to allow Josh Windass a scoring opportunity from close in. He squandered that by wildly scuffing his shot.
As with their previous meeting, Thistle gradually found a way in and Conor Sammon began to cause all sorts of problems, drawing a save from Jak Alnwick at his near post after side-stepping Fabio Cardoso down the inside left channel. With the break approaching, Alnwick again thwarted the Irishman, this time brilliantly leaping to his left to palm away a header from point-blank range.
Rangers began the second period with the same menace, and this time their pressure did yield results. That should have happened when Morelos was one-on-one with Scully at the edge of the box only for the keeper to get the slightest touch to send his low effort inches wide of the far post. From the resultant corner, Pena provided the goal Rangers’ efforts deserved. A Paul McGinn error that let Candeias run through on goal then looked like bringing the clincher, but he wildly blazed over.The Portuguese winger certainly later made amends, though. To the relief, no doubt, of his countryman in the dug-out.