Petr Cech has warned Chelsea that Saturday's opponents Southampton are the most dangerous they have been all season following the arrival of new manager Mauricio Pochettino.
Chelsea thumped Southampton 5-1 at St Mary's Stadium in the FA Cup in January but less than two weeks later they blew a two-goal lead as the Saints claimed a point at Stamford Bridge. That proved to be Nigel Adkins' last day in the charge of Southampton and Cech has been impressed by the improvements Pochettino has made since his arrival.
"In football, everything is different - you can have a first half that is completely different from the second half," Cech told cfc.com
"In the away game against Southampton we were very effective, taking our chances, and then at home we had a very good half - but the last half an hour of the game we allowed them to come back into it.
"You cannot do that in the Premier League.
"The teams are strong enough to grab the chance if you give it to them - everyone in the Premier League has that quality and will take it if you let them.
"They changed manager with Pochettino and they are more attacking, more organised with very good pressing which makes them more aggressive - and, in turn, more confident because of the success they've been having."
John Terry is available to manager Rafael Benitez - but his selection will be made with one eye on Monday's FA Cup quarter-final replay against Manchester United.
Benitez said it is "impossible" for players to peak twice in 48 hours so some rotation of the side is inevitable and Terry, after a season disrupted by a knee injury, is only likely to start one of them.
Chelsea's interim manager reported a clean bill of health following the international break and he is hopeful that Ramires (Achilles) and Gary Cahill (knee) could be fit for Monday.