I was going to do a topic on players who have under-achieved in their careers but the names that were coming to my mind were:
I know their are more but I wanted to focus on these ones.
Each one of these players either had a horrible head-to-head record against Monica or Steffi and/or choked a big match against them.
For instance Sabatini was never the same after Wimbledon 91 after she missed her shot with an open court which would have put a very close to winning the tournament. She was unable to get to a Grand Slam final again and was down 2-8 in the head-to-head afterwards after beating Steffi 5 times in a row. The French Open QF was the final nail in the coffin in 93. She should at least have one French title.
Anke Huber, was unable to beat Monica or Steffi and never took a set off Monica. Some of her worse losses came against these 2 and the pressure of being the next Steffi by the German media became too much. She should have won at least one Grand Slam but nerves always go the better of her.
Mary-Joe Fernandez well had horrible head-to-head records against both, she only beat Monica once and that was early in her career. Could have won the French in 93 but Steffi found a way to win. Unfortunately injuries was a major reason as well.
Jana Novotna, well what can I say?...Wimbledon 93 one of the biggest chokes in tennis history she was playing some of the best tennis I have ever seen (put in Wimbledon 97 as well, although she was never as close as she was in 93). her record against Steffi was very bad, she beat her 3 times (i am not counting philadelphia 96) and always seemed to have a mental block against her expecially at Wimbledon. She got her title but she was lucky she had Tauziat in the final, who was choking even worse than her
...she had all the talent in the world and Steffi even said that she thought that she would be her main rival.
So I have come to the conclusion that the reason is that players in those days had a lot more respect for their opponent when they played them and that caused them to get nervous. You don't see that too much now, more players are self-confident and they just play to win.
Or maybe just Steffi and Monica were too good, mentally and game-wise