Going to a back three worked wonders for Antonio Conte last season, but if Chelsea is to defend its Premier League title, another tactical shift must take place.
The start to this season has almost been identical to last term's title winning campaign last year for Chelsea, but it's going to be a rather different experience for Blues players at the end of this one if something doesn't change.
When Antonio Conte arrived at the Bridge following an embarrassing title defense which saw then fan favorite Jose Mourinho being given his marching orders, it went too well at the start.
Three victories on the spin in the Premier League put them as early leaders. But from three games later, it was crisis. A draw away to Swansea and then defeats to Liverpool and Arsenal set the alarms bells ringing.
But losing to Arsenal was a blessing in disguise. Conte played four at the back at the start of his tenure but soon realized it wasn't right. At halftime at the Emirates, 3-0 down, he switched it up to his preferred three at the back and Chelsea looked like another team from then on.
A total of 13 league victories on the spin, with the most notable being the away at Manchester City, turned their season around and led them to the title. But just like the beginning of last year, the side from west London are struggling.
Chelsea have already dropped eight points at home this campaign, two more than last campaign and they are only five games in out of the 19. That's certainly not title winning form.
The main issue? The formation.
Yes, it's Conte's preferred system and it worked wonders last year but that is when nobody else played that way. Brendan Rodgers implemented it at Liverpool while at the club but it didn't bring much success but with Conte and Chelsea, it did.
This put nearly all teams on red alert and by the end of the 2016/17 campaign, more than half of the teams in the Premier League were playing the system, and they still are.
It's been figured out; and that is why Chelsea are struggling. It was noticeable towards the end of last season, particularly away to Manchester United. Then again this season against Manchester City. Results of both? Defeats.
Now undoubtedly, N'Golo Kante is a massive reason as to why Chelsea enjoy so much success in the midfield and with his struggles with a hamstring injury, they are struggling. Cesc Fabregas can't play with just one another central midfielder, and Conte has seen that and has had to play with three in the middle instead to remedy it.
In the Champions League against Roma, David Luiz featured in Chelsea's midfield and he had to be taken off through an injury, but it then led to switching the system as Conte had no players to replace him with. Against Watford, the midfield was matched and they couldn't handle it. Yes, resilience and character was shown, but that papered over the cracks.
The defense is awfully shaky, and David Luiz's form has suffered compared to last season. He came back to the capital and looked a revitalized player. He was disciplined in defense and made himself a key player, but now, he has gone back to his usual tricks and is struggling.
Conte has worked with the four at the back system before, and Chelsea have the players to make it work. The majority of the squad were here when they won the title three seasons ago playing that system, so why can't they now?
If Antonio Conte was able to drill the three at the back system into them last season, under huge pressure after reports he could've been fired after the damaging defeat to Arsenal, why can't he do the same this year?
The Blues are too easy to read now. There's one way they play, Tottenham matched Chelsea up in the game where they could've gone 14 wins on the trot but they out fought them in the middle.
By the end of the season, they should be there in the race to claim one of the top four spots but they are going to find it extremely tough when they are coming up against the big sides, and even those lower down the table.
It may be too early too call, but when Conte switched it back to a defensive four against Watford, look what occurred. The Hornets even tried to close the game out at 2-2 when taking off Troy Deeney, an attacker, for Ben Watson who is a midfielder.
If Chelsea are being thought out by some of the 'smaller' teams in the Premier League, it's going to be a major issue if they get into the later rounds in the Champions League against the likes of Real Madrid and Barcelona.
Some food for thought for Antonio Conte.