September's 3-0 defeat to Arsenal was undoubtedly the turning point in Chelsea's season.Alexis Sanchez and Mesut Ozil single-handedly destroyed Antonio Conte's side at the Emirates Stadium that day to suggest they weren't ready to challenge for the Premier League.How wrong were we? Since losing to Arsenal, Chelsea have stormed to the top of the table and are now just six games away from winning the title.Only four points separate them from Tottenham in second, of course, but considering their remaining fixtures, it's unlikely they'll lose again.The players Conte brought in last summer have all been superb, namely N'Golo Kante, but it's the 3-4-3 formation he introduced that has really made the difference.Following the Arsenal defeat, Conte chopped and changed his side to facilitate three centre-backs (David Luiz, Gary Cahill and Cesar Azpilicueta) and two wing-backs (Victor Moses and Marcos Alonso).And the results have been staggering. Chelsea went on a 13-game unbeaten run in the Premier League to claim top spot and they haven't moved since.Defeats to Tottenham, Crystal Palace and Manchester United this year have threatened to derail their title bid, but they've made up for it by winning elsewhere and drawing only three times.So effective has Conte's 3-4-3 system been that even Arsene Wenger has started using it at Arsenal, who face Chelsea in the FA Cup final next month.But how exactly does it work? Conte must have put a lot of thought into the unorthodox formation, so it can't be easy to understand.Well, a video has emerged on Twitter unearthing just that - and it's absolutely brilliant.@toughtightcoach has compiled footage from Chelsea's FA Cup semi-final with Tottenham to explain what the players do in the 3-4-3 formation to make it so devastating. Check it out.

As Touchtight Coach explains, Conte has trained Chelsea's players to force their opposition out wide when possible and then perform a high press to limit options.

In other instances, when a Chelsea player is caught out of position, teammates quickly cover the space to ensure the 3-4-3 stays in tact.

Nemanja Matic is a particularly important component of the system. Whenever the opposition has possession, the Serbian is always looking to protect the back four and fill in when required.

There's too much in the video to be explained, so watch it and just admire Conte's brilliance.