Peterborough boss Gary Johnson admitted some of his players do not have the stomach for the fight away from home following the 2-1 defeat at Brentford.
Posh led with a hotly-disputed, twice-taken penalty from Grant McCann but Brentford drew level on 39 minutes when Craig Woodman rifled in a free-kick.
And Gary Alexander's diving header sealed victory for the Bees shortly before the hour mark to leave Johnson deeply frustrated.
He said: "Away from home we have a few shrinking violets and that's disappointing. It's something we're going to have to look at to see if they can pick themselves up and play away from home the way they do at home.
"We were very boyish all over the field. It was a Jekyll and Hyde performance and there are a few people in the side who I'm not sure can cope away from home.
"We'll see at the end of the season but I'm not sure if this group of players are the ones who can turn things round for us and that's the gauntlet I've thrown down after this."