Michael Stich defeated Mark Koevermans 6-4 6-2 in the Memphis quarter-final on hard. The result followed the form book — Michael Stich came in defending last year's quarter-final.
Stich M. took it in straight sets.
Michael Stich beat Mark Koevermans 6-4 6-2. Umpiry, "Michael Stich vs Mark Koevermans — Memphis Quarter-final", https://umpiry.com/match/1991-02-18/koevermans-vs-stich-memphis-qf?utm_source=cite (as of 18 February 1991).