You'll have heard it said thousands of times: consistency is key in football.
It's not a message which had found its way to Frank Lampard, however. The Chelsea boss has made a habit of chopping and changing his defence, using a whopping 20 different combinations in just 41 Premier League games.
Let's see how each fared.
1. Azpilicueta, Zouma, Christensen, Emerson
Games Played: 3
Goals Conceded: 7
This quartet gave Lampard a rough debut as they shipped four goals against Manchester United in the boss' first game.
They played the next two games too - a 1-1 draw with Leicester and a 3-2 win over Norwich - but that's when the rotation started going a little wild.
2. Azpilicueta, Zouma, Tomori, Emerson
Games Played: 3
Goals Conceded: 5
A 2-2 draw with Sheffield United, which included a Kurt Zouma own goal, wasn't the best way for this group to begin life together, and the Frenchman was dropped for the next game.
This group's next spell together was slightly more positive as they bagged a 2-1 win over Watford. No own goals this time.
Unfortunately, the positivity didn't last as they were soon beaten 2-1 by Manchester City, and that was that.
3. Tomori, Christensen, Rüdiger
Games Played: 1
Goals Conceded: 2
Lampard's first shift to a back three saw Fikayo Tomori, Andreas Christensen and Antonio Rüdiger play together, and Tomori bagged a stunning long-range goal to help his side to a 5-2 win over Wolves.
Rüdiger disappeared with an injury soon after.
4. Azpilicueta, Tomori, Christensen, Emerson
Games Played: 1
Goals Conceded: 2
This group's sole outing came against Liverpool, but they were powerless to stop Jürgen Klopp's side picking up a 2-1 win.
5. Azpilicueta, Tomori, Christensen, Alonso
Games Played: 1
Goals Conceded: 0
Marcos Alonso's first introduction to the starting lineup came for a comfortable 2-0 win over Brighton, but despite the good result, this group haven't lined up alongside one another since.
6. Azpilicueta, Zouma, Tomori, Alonso
Games Played: 3
Goals Conceded: 3
This group impressed in their first outing, a 4-1 win over Southampton, and they were rewarded by being allowed to keep their place for the following game, which saw Chelsea pick up a 1-0 win over Newcastle.
They again retained their spot for the next game, but Lampard was seemingly unimpressed with the 4-2 win over Burnley and never went back to this quartet.
7. James, Zouma, Tomori, Emerson
Games Played: 2
Goals Conceded: 1
Reece James' first Premier League start was one to remember as he helped Chelsea to a 2-0 win over Crystal Palace.
However, the optimism soon faded after this group fell to a 1-0 loss to West Ham.
8. James, Zouma, Christensen, Azpilicueta
Games Played: 5
Goals Conceded: 9
This is actually Lampard's preferred back line if the stats are to be believed. No group has played together more than this.
During their time together, we've seen a 2-1 win over Aston Villa, a 3-1 loss to Everton, a 3-0 win over Watford, a 3-2 win over Crystal Palace and a shocking 3-0 loss to Sheffield United.
Some real ups and downs from this bunch.
9. Azpilicueta, Zouma, Rüdiger, Emerson
Games Played: 1
Goals Conceded: 1
Emerson's return to the team wasn't a happy one as Chelsea were stunned 1-0 by Bournemouth.
Although, in his defence, Chelsea always seem to get thumped by the Cherries. It's one of football's unwritten rules.
10. Zouma, Rüdiger, Tomori
Games Played: 3
Goals Conceded: 3
This trio seemed like it could be the go-to for Lampard. Chelsea soared to a 2-0 win over Tottenham when they first joined forces, in what was probably the boss' most memorable game to date.
However, as is always the case, they couldn't keep it up. A 2-0 loss to Southampton followed, and the 2-1 win over Arsenal that followed was hardly impressive.
Time to go back to a four.
11. James, Zouma, Rüdiger, Azpilicueta
Games Played: 1
Goals Conceded: 1
César Azpilicueta was shifted over to left-back for January's meeting with Brighton, and he even managed to get on the score sheet!
However, Chelsea conceded a late equaliser as Alireza Jahanbakhsh fired home a spectacular acrobatic effort, and that was all she wrote.
12. James, Rüdiger, Christensen, Azpilicueta
Games Played: 4
Goals Conceded: 5
Another Lampard favourite, this group have played no fewer than four games together, despite the fact they've only won one game.
A resounding 3-0 win over Burnley got things underway, but the 1-0 loss to Newcastle a week later brought things crashing back down to earth.
After one week off, this group united once more and led Chelsea to a 2-2 draw against Leicester, but February's 2-0 loss to Manchester United was their last time together.
13. Azpilicueta, Rüdiger, Christensen, Emerson
Games Played: 1
Goals Conceded: 2
The week off that the above group had came as Lampard made a change for the visit of Arsenal, but his change didn't really pay off.
Despite an early red card for David Luiz, the ten-man Gunners roared back and managed to earn a 2-2 draw, with Chelsea unable to take advantage of the numbers.
14. Azpilicueta, Rüdiger, Christensen
Games Played: 1
Goals Conceded: 1
Another back three against Spurs, another win.
This time, the Blues managed a 2-1 win, with Spurs' strike coming courtesy of a Rüdiger own goal late on.
15. Azpilicueta, Tomori, Christensen
Games Played: 1
Goals Conceded: 2
Seemingly unimpressed with Rüdiger's error, Lampard threw him to the bench and replaced him with Tomori against Bournemouth.
Unfortunately, that didn't really work. Chelsea were 2-1 down at the hour mark and needed to take Tomori off to get back into the game.
Wing-back Marcos Alonso (who is far better than his evil twin, left-back Marcos Alonso) managed a late equaliser, rescuing a point for the Blues.
16. Azpilicueta, Zouma, Rüdiger, Alonso
Games Played: 2
Goals Conceded: 0
Tomori lost his place in the team the following week, and Lampard's decision looked justified as Chelsea stormed to a 4-0 win over Everton.
This group didn't join forces for another seven games, but when they did, the result was a solid 1-0 win over Norwich.
Two games, two clean sheets. Statistically, that's the best Chelsea have had under Lampard.
17. Azpilicueta, Christensen, Rüdiger, Alonso
Games Played: 3
Goals Conceded: 5
If you want to find a group who exemplify Chelsea's defensive woes, this is the perfect example.
Their first game was a nervy 2-1 win over Aston Villa, which was soon followed by an impressive 2-1 win over Manchester City.
Just as things were looking good, Chelsea fell to a crushing 3-2 loss to West Ham. The good times never last long.
18. Azpilicueta, Rüdiger, Zouma
Games Played: 2
Goals Conceded: 5
Lampard brought the back three out once more to try and withstand champions Liverpool, and it did not work. The 5-3 loss was, admittedly, pretty good fun though.
Somehow, they all retained their place for the crucial end-of-season meeting with Wolves, but they redeemed themselves as Chelsea picked up a 2-0 win to seal a spot in the top four.
19. James, Christensen, Zouma, Alonso
Games Played: 2
Goals Conceded: 3
Lampard turned to this group for the start of the 2020/21 season, and although things looked a little more organised, the results were the same.
A nervy 3-1 win over Brighton was followed by a timid 2-0 loss to Liverpool, but change was on the horizon. Summer signing Thiago Silva was ready to play.
20. James, Christensen, Silva, Alonso
Games Played: 1
Goals Conceded: 3
It wasn't the most convincing league debut for Silva, who made a costly mistake and had watched his new side concede three inside half an hour against West Brom.
Christensen also picked up a red card and will therefore be unavailable for the Blues' next game.
Could we have lineup 21 on our hands?
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Source : 90min