Jose Mourinho's substitutions worked like a charm as Paul Pogba and Zlatan Ibrahimovic came off the bench to combine for the winning goal and secure Manchester United's place in the FA Cup quarter-finals with a 2-1 victory at Blackburn Rovers.
United looked devoid of craft and decisiveness for much of the match at Ewood Park on Sunday and such a situation forced Mourinho's hand in the second half. Pogba and Ibrahimovic duly showed why the Portuguese entrusted the visitors' fate to them, as the Frenchman set up the in-form striker for a 75th-minute winner.
Blackburn gave a fine account of themselves in the first half and broke the deadlock with an exceptional goal inspired by Marvin Emnes and finished by Danny Graham.
United ensured the score was level at the break, as Marcus Rashford showed great composure to net his sixth goal of the season.
But that goal failed to bring about much of an improvement from United, though, and Mourinho - clearly unenthusiastic about the prospect of a replay - deployed Pogba and Ibrahimovic from the bench with just under 30 minutes to go.
Ibrahimovic then made the most of a Pogba pass 15 minutes from time to kill Blackburn's resolve once and for all, booking United's place in the last eight of the competition they won last season.
5 - All five of Paul Pogba's assists for Manchester United in 2016/17 have been for Zlatan Ibrahimovic. Telepathy. — OptaJoe (@OptaJoe) February 19, 2017
United saw more of the ball early on, but Blackburn looked a threat in attack and caused the Premier League side problems.
Emnes was particularly lively and worried Sergio Romero from distance with a fierce drive 16 minutes in.
Romero was helpless soon after, though, as Emnes terrorised United.
The Dutchman tied Marcos Rojo in knots, as he produced an effective step-over and then turned back on himself, before finally finishing the defender off with a fine reverse pass into the area and Graham clipped a lovely left-footed finish into the right side of the net.
But their lead did not last.
Henrikh Mkhitaryan caught Blackburn on the break and fed Rashford with an inch-perfect pass through the centre, which the striker latched on to and stroked home after coolly skipping beyond Jason Steele.
Another swift United counter almost resulted in a chance just before the break, though Mkhitaryan ultimately tried to take on too many defenders and was crowded out.
United looked rather more controlling of both the tempo and possession at the start of the second half, though they struggled to break down Blackburn's compact defence.
In response to United's continued frustration, Pogba and Ibrahimovic replaced Jesse Lingard and Anthony Martial respectively, and the Swede nearly made an immediate impact as he got agonisingly close to Ander Herrera's wayward shot.
Herrera produced a better effort 20 minutes from time, seeing a 20-yard drive go just wide of the bottom-left corner.
United finally found a way through Blackburn's stubborn defence, though.
Pogba lofted a brilliant pass over the hosts' defence from just inside the Blackburn half and picked out the run of Ibrahimovic, who brought it down and calmly placed his effort into the bottom-right corner.
Anthony Stokes did then see a late goal correctly disallowed for offside, but that proved to be the hosts' only chance to worry United, whose attempt to defend the cup continues.