With 15 World Snooker titles spanning an unbeaten 20-year period as World Champion and an entire career which contained only 4 defeats off level terms, all of which came in later life and all of which were inflicted by his own brother who was himself a multiple World Champion, it is difficult not to name him as one of the greatest players of all time. Ronnie O'Sullivan named him third greatest player, behind Steve Davis and Stephen Hendry. Indeed, until the 1980s, he was still generally regarded as the best, with even the next generation acknowledging the sentiment, as demonstrated by the famous snooker coach Frank Callan who in his book "Frank Callan's Snooker Clinic" published in the 1980s, compared the current best, Steve Davis, to Joe Davis in order to determine the greatest player ever. Neither Fred Davis, John Pulman nor Ray Reardon were mentioned. Callan also states that "many players who tried to emulate Joe's stance (which was unusually off centre due to left eye striking) simply gave up the game when they found they couldn't play like that". Such was the influence of Joe Davis. In Callan's own words; "His word was law". When taking into consideration the playing conditions of Joe Davis's time, it would perhaps be reasonable to assume that had he played in the modern era, with much faster cloths and the benefit of growing up in an era where from an early age a novice player has access to instructional tools such as books, video and more experienced players around him, he would have been an even better player. Joe Davis had to learn the game himself, in an era where Snooker was a game played for fun by Billiards Players, not a serious game. He wrote the instructional book "How I Play Snooker" which Steve Davis and his father Bill used as the basis for building the Six times World Champions technique back in the 1970s. Perhaps the best Example of the legacy of Joe Davis is the Shadow he still casts to this day over the modern legends of the game. Steve Davis, who holds the record for most Professional Tournament Wins and himself is generally regarded as the beginning of the modern game, has stated that if he could play against a player from the past, it would be Joe Davis, to "find out how good he really was".