Diamond (4-1) broke a personal two-game winless streak with the effort, in which the Indians scored three runs after errors by shortstop Brian Dozier and third baseman Trevor Plouffe.
The Twins left-hander allowed seven hits and didn't issue a walk while tossing 61 of his 93 pitches for strikes and lowering his ERA to 1.86 over 38 2/3 innings.
Justin Masterson (2-5) was touched for three runs on seven hits in a six-inning effort for Cleveland, which fell for the seventh time in nine games.
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