I grew up watching the big bouts of the 1970s and not just Ali fights - Carlos Monzon, Carlos Palomino, Alfredo Escalera, Little Red Lopez, Pip Cuevas, Wilfredo Benitez and, the best fighter who ever lived (IMO) Roberto Duran. I'm proud to say I watched fights like the Thrilla in Manilla, Chacon-Boza Edwards II, Holyfield-Qawi I and Ward-Gatti I when they happened. I've got enormous respect for boxers and their craft.
That said, a quality MMA guy would break a boxer apart in short order. Cyclone's being generous about a boxer lasting 90 seconds on the mat. My guess is he'd be choked out or thrown into a kimura within 15 seconds.