I think Pollard is going to be pretty good. When people think of him as a "web back", I don't think they realize he's bigger than Weber. Same height as Zeke, just less weight. He's fast on the field, which is more important to me. And he's tough to bring down for DBs, with his reception and route running experience, that's a valuable asset. He's also quick and experienced enough to cause matchup problems against LBs. He's a valuable piece in the new age NFL.
He didn't do a lot of running between the tackles in college, but he still averaged over 7ypc on almost 110 carries his last two years. Also means he has more tread on the tires.
Obviously if Zeke misses time, who knows. I have no idea if Weber or Jackson will be able to do anything. But, as a backup, if we're serious about taking advantage of matchups and using more shifts/motion, disguising roles, Pollard will probably end up being pretty successful for us.