Worth pointing out, but not an equal achievement to that of Seles. Taking a glancing peek at the players Seles faced in finals during her teenage rampage, we'll see she dispatched some quality opposition. She managed this during the time of 2 women's GOAT contenders.
Jana Novotná, Mary Joe Fernandez (worth pointing out she defeated K. Date earlier in that same '92 AO); Steffi Graf in 3 finals I believe (also beat Gabriela Sabatini in the same tournament); Arantxa Sánchez Vicario; Martina Navratilova (at the '91 USO Navratilova wasn't exactly useless).
Maureen Connolly: 9 slams won as a teenager
1951 US Open: bt. Shirley Fry
1952 Wimbledon: bt. Louise Brough
1952 US Open: bt. Doris Hart
1953 Australian: bt. Julie Sampson
1953 French: bt. Doris Hart
1953 Wimbledon: bt. Doris Hart
1953 US: bt. Doris Hart
1954 French: bt. Ginette Bucaille
1954 Wimbledon: bt. Louise Brough
- Fry and Hart both won the career Grand Slam.
- Brough was a 4-times Wimbledon champion, who Connolly twice defeated in straight sets in the W final.
- 2 slams won against players who never won a slam (Sampson, Bucaille)
- 7/9 slams won against very tough opposition (and the fact that you have not heard of them doesn't mean they weren't very tough opposition).
Monica Seles: 8 slams won as a teenager
1990 French: bt. Steffi Graf
1991 Australian: bt. Jana Novotna
1991 French: bt. Arantxa Sanchez Vicario
1991 US: bt. Martina Navratilova
1992 Australian: bt. Mary Joe Fernandez
1992 French: bt. Steffi Graf
1992 US: bt. Arantxa Sanchez Vicario
1993 Australian: bt. Steffi Graf
- 3 wins against Graf, no explanation needed.
- 1 win against Navratilova, but an old Navratilova. Still a good win.
- 2 wins against ASV, a borderline great, but the win over her at the French where she was a 3-time champ was impressive.
- 1 win against one-hit wonder Novotna.
- 1 win against a player who never won a slam (Fernandez)
On balance, I agree that Seles' competition was slightly harder.
Then again, Connolly's achievements were slightly greater: 9 slams vs. 8, including the CYGS (whereas Seles never looked likely to trouble Graf at Wimbledon).
Certainly they are in the same tier of greatness and it's not true to say that Connolly's achievements were "not equal to those of Seles"!