The USA midfielder has seized his second chance at Premier League football with both hands, and Coyle believes he will continue to improve.
"After picking him up for nothing, having had a few setbacks in his career, it's great to see him show his qualities," he said. "He wants to stay on the training pitch after every session and he's driving himself on to improve. There's no doubt he's doing that.
"The energy he shows, the level of his play, fans are reacting to that. We think the world of him, and the way he's playing at the moment is terrific for the club."