Conversation so far:
what occurred regarding ken rosewall in 1972?
From August 1972 players could enter almost all the tournaments they wanted and the real open era began.
what was a tournement he played in?
Rosewall won seven tournaments in 1972.
who was an opponent?
Mark Cox.
he did not defeat any opponents?
He lost in the second round of the 1972 U.S.
Open against Mark Cox.
What was his performance in the US open?
His best performances in 1973 were firstly his semifinal at the US Open.
what was the score?
CANNOTANSWER.

Question: what is a notable title he won?
Self-contained rewrite: What is a notable title Ken Rosewall won?