While it's unfortunate, it's also not an especially big deal. He should be able to recover from a stomach virus, and missing a few starts will help him get the rest he needs to come back strong. Alexi Ogando will replace him in the rotation, and we know full well Ogando is capable of being a strong starting pitcher.
As far as the loss of Ogando in the bullpen, it means we will finally see the debut of Tanner Scheppers. Scheppers has been putting up a strong season in relief for Round Rock, with nine saves, and a 3.72 ERA in 29 innings pitched. He's struck out an impressive 23.4% of the batters he's faced, against an even more impressive 4.5% walk rate, with a Pacific Coast League tRA+ of 131.