Armstrong was a good fighter and would have given Corbett a lot of problems stylisticaly. Ultimately he was not of Corbett's calibre however and this would likley dictate the outcome.
Corbett was way ahead of Armstrong in almost every way except size but strange to say stylistically he might give him trouble as Bob's problem was he was a bit-sorry lot-chinny. However by the time Bob was a contender Corbett's reign was over.
