I'm not sure how to translate the following sentence. if you could help I would be grateful.

しかし、彼は芹沢達也ーただでさえ常人ばなれしている頑丈さが、煉が絡むと人の域さえ超えると噂される男だった。

thank you in advance! Maybe more phrases will follow!

this is what I came up with:

But, he is the Serisawa Tatsuya – in addition to a sturdy nature, he was the rumored man of legend who surpassed the human limit by picking a fight with Ren!

this is next:

判官びいきというやつだろうか、健闘する芹沢に生徒の声援が集中する - i don't understand the first part of the phrase!

ただでさえ常人ばなれしている頑丈さ

ただでさえ = under normal circumstances
常人ばなれ　= far away from a normal person
頑丈さ　= strength, sturdiness

"His strength which under normal circumstances is far superior to an ordinary person..."

I don't have the context but I'm not sure that "pick a fight" is the best interpretation of 絡む. (Even if it is, Ren is the subject, not the object, so he'd be the one picking the fight!) I would say, "If Ren gets involved" or something like that...

"But, he is Serisawa Tatsuya -- he's a man whose strength is far superior to an ordinary person even under normal circumstances, but if Ren gets involved it's rumored that it would surpass the human limit."

thanks for the speedy reply!
ok next challenge:


判官びいきというやつだろうか、健闘する芹沢に生徒の声援が集中する - i don't understand the first part of the phrase!