Chelsea captain John Terry says Sunday's defeat against Arsenal will be hard to forget.
The Blues are yet to hit top gear this summer as they also suffered defeat against the New York Red Bulls last month.
They will face Fiorentina in their last pre-season friendly match of the season before hosting Swansea City in Saturday's Premier League opener at Stamford Bridge.
"I thought we were on top if anything," Terry is quoted as saying by Goal.
"These games are always a bit slow with players finding their feet and fitness, but it's disappointing we didn't win.
"Losing is just horrible in all aspects - forgetting the record [Mourinho's unbeaten run against Arsenal], it's a trophy that's gone now. It means a lot, because you've earned the right to be here so we're just disappointed.
"It hurts, it doesn't matter if it's a friendly or the Community Shield - it's a trophy at the end of the day.
"He's [Diego Costa is] a top player so he's going to be missed in all sides.
"It was a chance for Loic [Remy] to stamp his authority in the side, and [Radamel] Falcao second half, it's down to them boys to fight for their place.
"[They are] three great strikers and they'll all be fighting."