A back three worked for Solskjaer (and Lampard) so why is Chelsea boss stuck in his ways?

“The clean sheet was a big deal for us.”

Frank Lampard wasn’t just offering up superlatives after watching his team draw 0-0 with Sevilla on Tuesday evening. The pressure is on Lampard more than most managers. The club spent over £200 million in the window in order to close the gap between themselves and the rest of the pack, specifically Liverpool and Manchester City.

Early on in the season there were signs that the offensive set-up could really be something special. But defensively? That was a different matter entirely. Defending as an art isn’t the same as when Lampard himself was in his prime, but his team are taking it to new levels at the moment.

From the goalkeeping mistakes against Brighton, Liverpool and Southampton to some of the shambolic goals that were shipped against West Bromwich Albion and the Saints. Lampard has kept pointing to the fact that his team are allowing the second-fewest shots in the Premier League. That’s all well and good but if anything that speaks to a more worrying issue, that there are bad errors being made, or that the back line can’t stop anything, or both.

On Saturday Lampard and Chelsea travel up north to face Manchester United, a team with plenty of similarities. The two clubs both turned to former playing legends to help them usher in a new period following plenty of mistakes in the dugout, and certainly a lack of stability. Both sides haven't been afraid to splash the cash and both have really struggled to keep goals out. So far this season Chelsea have shipped nine in the league, United 12. The only teams to have let in more are Brighton, West Brom, Fulham and Liverpool. Of course it’s early days but it’s a worrying trend.

Whilst the United defence, and particularly David De Gea, look as if they have started to pick up a little bit (maybe) there are still questions over the Chelsea unit. Is that fair? Perhaps not given that Chelsea (three) have more clean sheets (two) than United. And whereas United's both came in the Carabao Cup Chelsea have one in each of the Premier League, Champions League and the aforementioned energy drink party.

But still the knives are out for Lampard, possibly because he has more history than Ole Gunnar Solskjaer. Last season Chelsea let in 54 Premier League goals, more than any other side in the top ten. United, by contrast, shipped 36, which was just three more than champions Liverpool.

Of course United,and players such as Luke Shaw, Harry Maguire and De Gea, have had their fair share of early struggles. But the switch to a back three, with Axel Tuanzebe and Alex Telles coming in, paid dividends in Paris in mid-week.

What’s ironic of course is that Lampard turned to a similar system before, showing a degree of tactical flexibility that he hasn't displayed so far this season.

Last season he could see the problems his team were having and in order to try and bring some stability he moved to three at the back. Was it perfect? No, not at all, but it gave the team a little more solidity.

So far he hasn’t done that, does he believe that new signings Ben Chilwell, Thiago Silva and Edouard Mendy are enough to prevent that? The draw against Sevilla might suggest yes but United, and particularly Marcus Rashford, will pose more of an attacking threat.

And Chelsea have the players to do it. Reece James is a perfect wing-back and Chilwell could play centrally or out wide. It also offers the opportunity to bring captain Cesar Azpilicueta in and help protect Silva or Zouma from Rashford's pace a bit more. Of course it means sacrificing an attacking player but in a big game like this is that a problem? They were lucky Liverpool only scored twice, they don’t want United doing to them what Spurs did to United a couple of weeks ago.

When Rashford is at his best he’s nearly unstoppable. You don’t have to be at your best to get chances against this Chelsea defence at the moment. Just look at the way they've been embarrassingly opened up by West Brom and Southampton.

Don’t forget either that Rashford might have new signing Edinson Cavani for company, that’s another hard-working forward who can make lives difficult for centre-backs. With an extra player to draw attention all of a sudden space starts opening up for Rashford, which will spell trouble for Chelsea.

Perhaps Lampard is too afraid of leaving out one of his expensive attacking stars, either for fear of a reaction or simply because of what it might take away from his team as a whole. But as Azpilicueta pointed out after the draw with Southampton they cannot constantly be relying on the attack.

“This is a problem we have to fix collectively and individually. Sometimes you can get away with it but you cannot rely every game on having to score three goals."

Lampard has to be careful, the goodwill towards him from both board and supporters will only last so long. This is absolutely not the time to panic, but he and his team need to prove that Sevilla was not just a one-off.

It’s hardly likely to end up defining either team’s season but it will tell us a lot about where they are. Are Silva and Mendy the key for Chelsea to be solid defensively? Or are there deeper problems. Have United and Solskjaer found a formula that can survive long-term and can finally bring them some consistency? It promises to be a fascinating encounter.