I'm looking for a single word (noun), rather informal, that would fit here:
The team is getting a lot of … for losing the last two matches`
"you must be strong enough to take the flak if things go wrong"
While I certainly agree with @Colin's answer of "Criticism" as perhaps the most common word to fit your sentence, you specifically asked for an answer that is "rather informal." For that case, I would use the word "crap." Note that this is extremely informal, bordering on the vulgar or offensive. It's something that would be said to your friends, but never to a broadcast audience or printed in a newspaper.