A band is only as good as the drummer. Seriously.
I just had a couple of shows about a week apart. One of them was with some guys I've been doing originals with, but for a church BBQ we threw together a set of covers. The drummer is tight, solid on tempo, has a deep pocket, accents when he needs to. One rehearsal and we hit the groove perfectly and it was a great set.
The other was with a cover band I've been trying to get launched. It was, frankly, just barely over the threshold of an acceptable bar band. Barely. Tempo pushing and pulling all night, hammering away at the drums with no sense of pocket, has a hard time sustaining fast tempos of punk-style songs (we had some pop-punk like The Middle). The cadence of Seven Nation Army threw him every time (daaaah da DA DA DA daaah daaah - he would drag the beat back on the DA DA DA every time, even with me stamping my foot in time as I played to show him where it was). We managed to avoid ever actually having a complete train wreck and the joint hired us back, but it's supposed to be a dance band playing wall-to-wall dance music and we only got a handful of people up and dancing on half a dozen songs.