Pity Will Vaulks. He followed his instructions to the letter for 45 minutes.
Vaulks stuck to Jonjo Shelvey like glue.
Then it happened. Vaulks, and Rotherham United, became unstuck.
Newcastle United 4-0, though the scoreline was harsh on Paul Warne’s team.
Vaulks, asked to man mark Shelvey, had to stand 10 yards away when the Newcastle United stepped up to take a free-kick in added time at the end of the first half.
The delivery found DeAndre Yedlin, whose first-time cross found Daryl Murphy.
Murphy did the rest. And that was that.
Let’s be clear. Rotherham, the Championship’s bottom club, made life difficult for Newcastle before the break on Saturday.
And had it not been for a superb first-half save from Karl Darlow, the scoreline would have been different.
Darlow somehow got across his goal to deny Jerry Yates to atone for a handling error which had gifted Rotherham possession in United’s box.
Newcastle had prodded and probed, but they didn’t look like scoring.
Ayoze Perez couldn’t find a team-mate with one pass, while he shot over after Murphy intelligently flicked the ball to him in space.
Rotherham’s gameplan was working.
And Shelvey, thanks to Vaulks’ close attention, wasn’t able to dictate the game.
But Vaulks couldn’t stop the free-kick. And Rotherham couldn’t stop Yedlin and Murphy capitalising on his stunning delivery.
Murphy’s signing from Ipswich Town last summer didn’t capture the imagination on Tyneside, but the striker has now scored in each of his last three appearances.
The 33-year-old, in the shadows for the first half of the season, is enjoying his time in he spotlight.
Murphy wins his headers, holds the ball up and knows how to score at this level. His £3million fee looks to be money well spent.
The second half was a different story. United tore the visitors apart with their pace.
Warne, Rotherham’s interim manager, spoke to a huddle of journalists on the touchline.
He was cold. He was frustrated.
Warne admitted his team couldn’t cope with the pace of Yedlin, Matt Ritchie and others.
As they chased the game, gaps opened up, and Newcastle went on to win comfortably.
Ritchie made it 2-0 with a close-range finish early in the half after goalkeeper Richard O’Donnell palmed a shot into his path, and Perez netted a third goal in the 59th-minute after Yedlin crossed from the right.
Yedlin, in particular, was a revelation.
With Vurnon Anita sidelined for around two months with an ankle injury, Yedlin’s performance at right-back was timely.
And Ritchie capped a comfortable win with a fourth goal after Shelvey found him with a pass.
Benitez was able to give valuable minutes on the pitch to Sammy Ameobi and Jamie Sterry, back from their respective loan spells at Bolton Wanderers and Coventry City, in the second half.
The result took United back to the top of the Championship.
Brighton and Hove Albion had beat Sheffield Wednesday the night before to briefly lead the division.
Things got better for Newcastle after the game when Barnsley came from behind to beat Leeds United at Oakwell.
The gap between first and third-placed Huddersfield Town is now nine points.
Leeds are a further point adrift. So far, so good.
United have had a wobble, but they are still on top, though Brighton play their game in hand against Cardiff City tomorrow night at the Amex Stadium before the FA Cup’s fourth-round weekend.
It’s still looking like a two-horse race, though Benitez, keen to guard against any complacency, has repeatedly pointed out that there are seven games in April.
That’s 21 points. The league, he feels, won’t be decided until then, though few will bet against Benitez’s team and Brighton taking the Championship’s two automatic promotion places.
In the meantime, the worry is that Newcastle are still too reliant on Shelvey, whose enforced absence led to that wobble.
Newcastle still need to strengthen in this month’s transfer window. Benitez needs another midfield option or two.
If they lose Shelvey to injury or suspension in the second half of the campaign, they will again become vulnerable.
Benitez knows this, and that’s why he’s pushing for reinforcements in the window.
And United’s manager wasn’t getting carried away after watching his team beat a team which has won just 16 points so far this season.
That said, this has been the kind of fixture which Newcastle have struggled to win this season.
This game was a struggle for 45 minutes.
But Shelvey – who had set up all three goals in the club’s 3-1 FA Cup win over Birmingham City at St James’s Park three days earlier – is a player capable of unpicking any team.
Vaulks did his best to stop him in open play, but he couldn’t stop him picking out Yedlin with a free-kick.
With Shelvey, United look unstoppable.