The alien wrestler is said to be a giant. However, he appears to be only a couple of inches taller than John Robinson, as is the second wrestler. So either they are of average height or John Robinson is a giant as well.
Will reveals that his father, Dr. John Robinson, lettered in 3 sports while in college and was offered an opportunity to play professional football. Perhaps fencing was one of the 2 other sports in which he lettered in.