“It is messy, and it is tricky,” said Steve Flink, an American tennis historian.
First, there is the amateur era, which lasted until 1968 and prohibited professionals from taking part in the four major tournaments: the Australian Championships, French Championships, Wimbledon and U.S. Championships.
Until 1968, leading men’s players — like Jack Kramer, Ken Rosewall and Rod Laver — would often turn professional after making their mark in the amateur game, which meant Grand Slam events seldom featured all of the best men in the world, only the best “amateurs,” some of whom received under-the-table payments to help them afford to remain amateurs.
The hypocrisy helped lead to change, but it also skewed the record book. Mr. Laver, who co-won all four major tournaments in 1962 and 1969, was ineligible for Grand Slam play for five full seasons in between.
That was not an issue in the women’s game, which had no professional circuit.
“In women’s tennis, there really should be no distinction between amateur and Open era because everybody played,” said Martina Navratilova, who became one of the greatest champions of any era by winning 167 WTA Tour singles titles, including 18 Grand Slams, and 177 doubles titles.
But leading women in the earlier years sometimes cut short or interrupted their competitive careers to raise families, depriving tournament fields of established stars.
There have also been plenty of major tournaments since 1968 with diminished fields for women and men.
The first open Grand Slam tournament — the 1968 French Open — was disrupted by protests and strikes and was nearly canceled. Some stars chose not to come, including Arthur Ashe, John Newcombe and Margaret Court, the Australian who holds the record for most Grand Slam women’s singles titles, with 24. Other players struggled to reach Paris.