If you've had a similar experience, I'd love to read about it. If you have more constructive advice, please share.
I had a couple of friends challenge me for a video for their YouTube channel. They were doing a fitness series and were trying all sorts of things out.
I'm a white belt in the gi, but have an extra four years of no gi grappling. We grappled no gi, 5 minute rounds. I took them on one after the other. None of them have any experience whatsoever.
There were three of them. I took on the largest first (about 100kg/220 lbs). He actually had pretty good instincts (from lots of play fighting with his brothers, apparently) and defended for a minute or two... Them I tapped him about 5 times.
The next two were only slightly heavier than me (approx 80kg/175 lbs). They both got tapped 12 times in 5 minutes.
I'm a white belt, lighter than all of them, had already trained that day, and was specifically going soft so I didn't hurt them.
The guy you're grappling is bigger, and training a little, so don't be surprised if he gives you a bit of trouble at first, but I'm almost certain you'll completely fuck him up. Especially if it's just a normal match.
If it'd just been normal matches, instead of 5 minute rounds, none of my friends would've lasted more than a few minutes. The two smaller guys both got tapped within thirty seconds.