Why did Rowland-Smith get the win last night?

Felix Hernandez left the game after 4 2/3 with an injury and a 5-1 lead. Corcoran relieved Hernandez and finished the 5th and pitched the 6th with the lead still 5-1. Rowand-Smith pitched the 7th and 8th and got the win with the score still 5-1 after the 8th.