It's older than you might think.
Ron M. wrote,
"The phenomenon of using the word 'verse' instead of 'versus' seems relatively recent, but to this 56 year old's ears, it's driving me nuts. I first started hearing this about 15 years ago when my sons were interested in Wrestlemania. They and their friends would be talking about who was wrestling who and would use the word 'verse.' I would gently correct them and tell them the correct word is ‘versus’ ... Latin for 'against.' It seems like suddenly this mis-usage is rampant. I'm actually hearing professional sportscaster making this error!"
Jackie also provided an example. She wrote,
"Before a soccer game ... my kids say, 'we are versing' such and such team. I would love to know what kid started using the verb form of 'versus,' but it certainly stuck!"
Versing: It Starts with the Children
When I first started getting questions about "versing" to mean "playing," I thought it might be a regionalism, like how people are more likely to say "spendy" in Oregon than in Florida; so I surveyed people the Grammar Girl Facebook page, and what I found instead is that it's an age-related phenomenon. People say "versing" everywhere, but they're nearly always kids. Although it's not unheard of among older people, my Facebook followers reported hearing it most often from elementary school kids.
It seems to be especially common in Australia and New Zealand. It could just be a statistical blip because I have fewer followers in those countries than in the U.S., but Keryn from eastern Australia wrote, "'Verse' is a very common formulation here, especially among TV sports journalists. I even saw it on a billboard outside our local football stadium—Team A 'verse' Team B."
Kids say 'versing' everywhere. (Red=a person reported hearing "versing." Blue=a person reported they had never heard "versing.") See the whole international map.
Versing: How Old Is It?
"Versing" is not as new as many people think, although we'll get to the reasons that it might be spreading in a minute.
As Ron noted, his kids were using "versing" 15 years ago. The oldest report of hearing it comes from Bob P., who says his sister used it more than 30 years ago in New York when she was in middle school. He wrote, "She would almost exclusively use it in the past tense, as in 'We versed Mrs. Smith's class in a spelling bee.' It was also typical for her to use it when forms of the verb ‘to play’ seemed wrong—you wouldn't really 'play' another class in a spelling bee, but you would 'play' them in kickball, which is what she would say."
Versing: I Thought My Kid Made It Up
A lot of parents who commented seemed to think that their kid made it up; they didn't realize that it is widespread. [One possibility is that 20 and 30 years ago, kids did occasionally make it up by mistaking the preposition "versus" for a verb.
It's actually quite logical for kids to think that if "Sue dances with Joe" goes with "Sue is dancing with Joe," and if "Squiggly sees Aardvark" goes with "Squiggly is seeing Aardvark," that "Mrs. Smith's class versus Mr. Javier's class" leads to "Mrs. Smith's class is versing Mr. Javier's class." "Versus" sounds like a verb to them, not the preposition that it is.
So it's reasonable to think that every once in a while, kids did make this mistake and used "versing" for a while until someone corrected them or they got older and realized it was wrong.