Infielder Daniel Robertson was recalled from Triple-A Durham in a corresponding move.
Diaz is hitting .286 with 11 home runs and 31 RBIs in 56 games this season, making 31 starts at third base and 14 at first base. He also has started 11 games as the designated hitter.
He had been out of the lineup for the first two games of the second-place Rays' series against the first-place Yankees, both of which Tampa Bay lost. The Rays enter their game on Wednesday afternoon against the Yankees 2 1/2 games back in the AL East standings.
Robertson, who is hitting .205 with two home runs and 15 RBIs, had been demoted to Triple-A last weekend when the club recalled right-hander Jake Faria.