Obviously Oliver McCall . Although he probably knew something b4 sparing Tyson or otherwise how did he get it ?
1 reason he was so good at that was gift decisions and avoiding anyone ranked in the top 10. More boxers should take a leaf out of his book, eh?
Not an all time great fighter,necessarily,but certainly a very good one,comes to mind. Ken Norton. He learnt his trade by sparring with the great Smokin' Joe. Sparring with great fighters is indeed a good way of learning the trade.