Serena Williams defeated Klara Koukalova 6-2 6-2 in the USA vs CZE round robin on hard.
Williams S. took it in straight sets.
Williams S. and Koukalova K. faced 4 of the same opponents in the last 12 months. Williams S. went 4–0 (100%) against them, Koukalova K. 0–4 (0%). Williams S. came out better against 4 of 4 comparable opponents, Koukalova K. against 0.
Only 4 common opponents — small sample, treat as indicative.
Serena Williams beat Klara Koukalova 6-2 6-2. Umpiry, "Serena Williams vs Klara Koukalova — USA vs CZE Round Robin", https://umpiry.com/match/2003-04-26/koukalova-vs-williams-usa-vs-cze-rr?utm_source=cite (as of 26 April 2003).