IF the aim for Newcastle United in this season’s FA Cup was to prevent Rafa Benitez’s squad from feeling the strain that could damage attempts to stay in the Premier League, then it’s safe to assume things didn’t go according to plan.

First thing’s first and Newcastle have booked a fourth round place, where they will face Watford, for only the fourth time since Mike Ashley took control of the club in 2007, despite clearly treating it differently to how the club’s travelling band of 2,700 fans did at Ewood Park.

But in not fielding their strongest team for either of the two games against Blackburn, of the Championship, they ended up playing for longer and suffering more injury woe than Benitez would have liked four days before a crucial relegation tussle with Cardiff City.

Not only did Newcastle have to add an unwanted replay to their schedule, they were forced to play half an hour’s extra-time having allowed Rovers to come from two goals down to level in the first half.

Throw in the fact that Ciaran Clark and Jamaal Lascelles had to go off with injuries, and Isaac Hayden is likely to be treated after suffering a knock too, and you can’t help but sense a degree of irony given how Benitez, who had already lost Jonjo Shelvey in the competition, wanted to rest players in the FA Cup.

But in the end Newcastle did avoid a FA Cup shocker.

It was all going smoothly when Newcastle young guns Sean Longstaff and Callum Roberts put them two up inside 22 minutes.

But another of the club’s academy graduate,s Adam Armstrong, pulled one back for Blackburn in the 33rd minute before Darragh Lenihan’s header on the stroke of half-time was how it stayed for the rest of the 90 minutes.

Newcastle found their feet after the restart to finally finish off the job when Joselu tapped in a rebound from Fabian Schar’s long range effort, despite a strong hint of offside in the 105th minute.

And less than two minutes after the interval substitute Ayoze Perez crashed in a fine fourth to set up the Watford date, when Benitez must surely consider playing a strong team.

If Benitez was keen to make another statement, which many have accused him of doing at times with his selection, then it was a big one beforehand but he got away

Eight was the number of changes he made for the second time against Rovers in ten days, so the travelling supporters must have already feared the worst before a ball had been kicked – particularly with the sight of Fabian Schar lining up in midfield.

Defensively-minded Schar, one of Benitez’s summer signings, had not started at Chelsea on Saturday, when Newcastle slipped back into the relegation zone, teeing up this weekend’s important duel with the team sitting above them in the table, Cardiff.

That Cardiff match is what Benitez will point to as his reason for leaving his key men out, but that did provide an opportunity for others.

A number of players failed miserably against Blackburn at St James’, so the onus was on a few others this time.

Roberts, for one, made his full debut behind striker Joselu and he didn’t take long to make an impression. Well before he found the net himself, and with one of his first touches, the youngster rolled a pass into the feet of Longstaff.

There was still plenty to do and Longstaff, with bodies in front of him, tried his luck from 20 yards and was rewarded with a big deflection that ended with the ball finding the inside of David Raya’s right-hand post inside 60 seconds.

It was the perfect start to settle nerves for the visitors and, with the Newcastle fans celebrating wildly before belting out their now customary anti-Mike Ashley chants, that led to an increase in confidence.

Even when Blackburn broke forward in the first 20 minutes, the visitors’ rearguard did what it had to do. Federico Fernandez and Clark made it tough for Ben Brereton, Danny Graham and Armstrong in attack.

There were a couple of harmless efforts from distance that failed to test Freddie Woodman, while Raya was the busier. He had already had to make a strong stop to deny Matt Ritchie, one of the few survivors from the trip to Stamford Bridge, before the second arrived.

Jacob Murphy was next to go close when he tested the goalkeeper at his near post, and the rebound fell kindly to the winger out wide.

Murphy, hugely disappointing in the first meeting of these teams, darted beyond his marker Amari’i Bell before placing a dangerous ball into the six-yard box for Roberts to meet with a perfect volley inside the keeper’s left.

Blackburn, too, made changes, five of them, and didn’t look as confident initially as they did on Tyneside despite winning at the weekend.

Former Middlesbrough manager Tony Mowbray had the worry of a bug running through his squad to contribute to his selection, including leaving out key man Bradley Dack, but Newcastle still had to perform and did for a period.

But just after the half an hour mark Newcastle’s previously resilient defence let the standards drop. Graham, a boyhood Magpie formerly of Sunderland and Boro, played in Armstrong and he did the rest, with a lovely chip over Woodman to pull Blackburn back into it.

By the time the whistle had blown for the break Blackburn had levelled.

A Harrison Reed corner was lofted perfectly into the centre of the box where Lenihan – who had set alarm bells ringing moments earlier by heading an identical chance over - climbed highest to power a brilliant header beyond Woodman’s outstretched right hand.

The signs for Newcastle soon got worse. Having replaced Ciaran Clark at half-time, Lascelles pulled his hamstring with his first run and the biggest surprise was that he stayed on the pitch for a further ten minutes.

And as he hobbled around, he was unable to clear his lines properly and Ben Brereton almost benefited when he drilled an effort across goal. Benitez, clearly animated and frustrated, then took him off.

After that neither team showed the quality required to get the tie wrapped up before full-time, and not even referee Lee Probert helped when he didn’t react to a strong penalty shout after Joselu was brought down by Lenihan.

Newcastle did see substitute Isaac Hayden nod a Ritchie corner against the post, while Blackburn finished the stronger without seriously testing Woodman. The extra-time what many expected, predicted and feared beforehand arrived - and then Newcastle finally progressed.