Well we all know what the outcome would be even if he spent 20 years doing Aikido. The boxer would have owned him!
Not necessarily so, but in many, if not most cases, absolutely.
One example (if you believe the story) is Gozo Shioda taking on a boxer who had defeated one of his students. Shioda Sensei, on the other hand, seemed to have little trouble. The details give some idea of one way to handle such a situation.