On July 31, 1989 — 1989 – The Twins trade last year’s Cy Young Award winner, Frank Viola, to the Mets for five players, including pitchers Rick Aguilera, David West and minor leaguer Kevin Tapani. Viola is the first Cy Young Award winner to be traded during the following season. Tapani will blossom into a Cy Young Award contender in 1991.
Source:
Baseball Reference July 29
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