1. That TBB was probably weak b/c he was fighting in his own village
2. Suigetsu was in the form of water. Water > TBB
3. Suigetsu had a field advantage
It's crazy he stands up to a TTB from the hachibi whereas orochimaru would have died if he got hit with a TTB from 4 tail naruto.
Not to mention he was scared shitless everytime he got manga time . He survived it off of pure luck just Luke madara surviving gais final attack.