Not really. Up to this stage of the season the Bills overall offense is top 5 and no slouch. They were going to be a test for the Brown's D.
The Bills got 14 pts off of two unfortunate plays.... a PI call on Hayden that put the ball on the 1 yd line, and a rookie mistake by Mingo who didn't seal the corner, force the run inside, and allowed Spiller to get outside (54 yd TD run). It happens. They showed the defensive coach talking with Mingo afterwards on the sideline about what he did wrong. You learn from it.
You lost both starting QBs, and IMO that was the difference in this game (more so for the Bills). The Browns had Weeden, who has experience and stepped it up. While the Bills had to rely on an undrafted rookie making his first career start (Tuel).
I'm not afraid to admit that it could have been a different outcome if the Bills hadn't lost QB Manuel. I'm very impressed with this kid.