Departing Chelsea coach Steve Holland says manager Antonio Conte always had plans going with three at the back last season.
Conte's decision to abandon a back four following the Blues' 3-0 defeat at Arsenal on September 24 triggered a run of 13 consecutive wins which catapulted them to the top of the table.
Holland left his role as Conte's assistant last month to take up a full-time No2 role under Gareth Southgate – having previously divided his time between the two – and he said: “I spoke with Antonio at the end of the previous season and, like Gareth now, he'd made observations on what he'd seen, what he thought needed to be done and also spoken to people to get that reinforced. Gareth has gone through that same process.
"Antonio said to me at the end of last season 'I think the team can play 4-3-3 with wingers wide, I also think they can play 4-4-2 with wingers wide'. Then he asked me how often they'd played with three at the back in my time, he asked me that question.
"I said never, Chelsea have never played three at the back. He said 'I think there is a 3-4-3 there as well with the players we have, but because they've never done it before it's not going to be the first thing I visit'.
“We played Real Madrid in the summer, 4-4-2 with wingers wide which we'd trained for a couple of weeks. At that point he decided that wasn't the best road, he then went 4-3-3, which is what we did for the first three games of the PL season going into the international break."
Source: tribalfootball.com