On Sunday night at the Metro, Karen O was back in Chicago and ready to rock. Or was she? Yes, she was draped in more ghastly attire than usual, with eyeballs and feathers strewn all over her red tank top. And she did have a significantly smaller beer gut than the last time the Yeah Yeah Yeahs came through the Windy City. But, alas, one thing prevented this New York trio from giving the kind of show they were born to put on: a 103° fever. Befitting a band whose 2003 debut is entitled Fever to Tell, Karen O’s fever certainly did tell the crowd one thing: a band whose live performances depend so much on the lead singer’s antics, screams, crouches, wheezes, and screeches should reconsider performing when Karen O is out of commission.

And, oh man, does it hurt to have to say that. I never thought that the Yeah Yeah Yeahs would ever earn my ridicule, considering the obsession I have with their every chord. But my justification makes sense (at least I think so). If 1,000 or so 18-and-over folks traveled from all over Chicagoland to make it to a late (10 p.m.) show on a Sunday night and paid $14 to do it, then they should see a concert worth the trek and the Monday morning hangover, right?

Since the YYYs didn’t take the stage until around midnight, most of the crowd was well into their third drink by the time Nick Zinner appeared on stage, guitar in hand, to announce that Karen O was running a high temperature. That’s also around the time that I was well into my sadness over the fact that Karen O’s groveling would be less animated, her shouts of “chow chow chow” in “Date with the Night” would be less ravenous, and her sex appeal would be much less overt when she’s sweating bullets more because of sickness than because of her hip shaking. I was right in my predictions.

Many things can be said in the band’s favor, however. Despite feeling so ill, Karen O made an obvious attempt to show the crowd that she knew she couldn’t perform like she wanted but would still try her hardest. Her decreased lung capacity and frequent breaks between sets didn’t hurt—and maybe even improved—the band’s quieter songs like “Maps” and “Modern Romance.” Mainly because her voice is often a tempo-keeper in addition to the drums, the timing in many of the faster tunes such as “Miles Away” and “Art Star” were thrown a bit off. The diva did preserve the scratchy growl of “aaaaaart staaaaar!!!!” even if it did require all the strength she could muster.

Most importantly, the boys in the background—guitarist Zinner and drummer Brian Chase—stepped up to make the music itself worthwhile. Chase drummed with the energy of a little boy just introduced to his parents’ pots and pans but, unlike an amateur, hit the beats right on. Zinner’s chords echoed flawlessly and doused the walls of the Metro in rougher, heavier splashes. The licks and bangs resuscitated Karen O’s less provocative and energetic vocals—something few bands, indie or not, can achieve. I liken the teamwork among the band members to that of a family, with these “brothers” bringing their sister a spoonful of sugar to help the medicine go down.

The concert provided a glimpse of the Yeah Yeah Yeahs to come. Originally, on their self-titled EP and the Machine EP, the band’s sound was raw, under-produced, and scandalous. The aforementioned Fever To Tell, the band’s only full-length release, caused battles among several record labels from which Interscope emerged victorious. While the LP features fancier studio sound, it maintains the same garage punk instrumentation and wild vocals the band, at its best (and healthiest), produces in spades.

So what’s in store for these indie babies? Apparently a lot, if the new songs they played on Sunday night are any indication of what their upcoming album, still very much in the works, will sound like. The songs were harder, darker, and, put simply, more solid rock than punk. The consistent interaction between Zinner and O in these songs presented more than savory songwriting—it showed stronger alliances among the band members and the capability of performing as a whole rather than as a she. And for that, my friends, it was worth watching Karen O nurse copious amounts of water rather than beer, and be diseased rather than drunk.

So, maybe it wasn’t all that bad. Perhaps I just over-anticipated the show and exaggerated the amount of energy a lead singer could have night after night of screaming, partying, and being awesome. Still, I remain hopeful of what’s to come for the Yeah Yeah Yeahs in the future, and trust that Karen O, Zinner, and Chase will return to Chicago in full force the next time around. After all, Karen O did say, “We love playing your fucking town.”