What was in 20-year-old Kate Upton's plastic cup at the Detroit Tigers game?

Left to right: Sports Illustrated Swimsuit models Genevieve Morton, Catrinel Menghia, and Kate Upton. (Reuters)

Kate Upton was doing the cat daddy dance again.

This time, she was caught on camera at a Detroit Tigers game, in star pitcher Justin Verlander's box, no less.

VIDEO: Upton's (formerly) banned Youtube cat daddy dance.

But the Sports Illustrated model doing the dance that got banned from Youtube, and her being linked to the hardest throwing pitcher in baseball, isn't the story here.

It's what was in the plastic cup while she was doing the cat daddy that has people talking.

Upton is only 20, and it sure looked like she was drinking a brewsky. That's a no-no in Michigan, where the legal drinking age is 21.

VIDEO: Watch Upton at the game - what's in that cup?

Tiger stadium says it takes things a step further, carding anyone who appears to be under 30.

Upton sure appears to be under 30.

Upton's rep told TMZ the model was definitely not drinking beer at the game, but would not divulge what was in the cup.

HOT SHOTS: Kate Upton.

According to the Alcohol Policy Information System, the only time a person under 21 can legally drink alcohol in the state of Michigan is if they are involved in an undercover sting operation, or if they need to as part of their education (read: culinary school).

If Upton is in culinary school, she has been skipping a lot of classes. And if she's doing undercover work, she is the most photographed undercover operative in history.

Regardless of her beverage, some Tigers fans are eager to nip any Upton/Verlander romance in the bud (or Bud Light).

Following her appearance in Verlander's box, the fireballer went on to pitch in the All-Star Game, where he was shelled for five runs in the first inning, helping to send the American League to an 8-0 defeat to the National League. Upton -- a Michigan native -- and Verlander were then reportedly spotted in a Detroit bar and an Aerosmith concert.

Jessica Simpson was famously booed by Dallas Cowboys fans when she was dating Tony Romo, as whenever she showed up at Cowboys Stadium, he played awful. Talk of a similar "Upton Effect" is already gaining momentum in Tigers online forums.

If she's interested in retaining her good standing in her home state, Upton had better hope Verlander pitches better in his next start.