The Saints gave it a good go in the opening half hour of the contest, before the Blues took over.
A red card changed the game, with Axel Disasi, Christopher Nkunku, Noni Madueke, Cole Palmer and Jadon Sancho all scoring for Chelsea.
Post-game, Bree said: "It was a strange game, obviously, we conceded five goals. That's a problem. It's a weird one because I want to come here and say at times we played some really good football.
"(At times) we cut through them and caused some problems but I think when they got the third goal, and we were down to 10 men, I think it was always going to be an uphill battle.
"We tried hanging in there and making a game of it. If we put away a couple of the chances we had, maybe it could have been a different game.
"I think 5-1 at the end of the day probably flatters them a little bit."
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