Positives: Despite throwing his mid-to-high-80s heater 70% of the time, Vargas gets surprisingly decent mileage out of the pitch. It's nothing spectacular, but of the four lefties in the bullpen race, his fastball is easily the best.
Vargas throws a decent slider and change as well.
Like Olson, French, and Seddon, Vargas doesn't miss bats, but he does have excellent control, walking just 2.36 batters per nine last year.
Weaknesses: Vargas doesn't have much of a platoon split, so he wouldn't make a great lefty specialist. He fits better as a long man.
He works up in the zone a lot, leading to high fly ball and homer rates, even at Safeco Field.
Overall: Vargas is the best pitcher of the four lefties vying for relief spots, but is ill-suited for situational work. He's a square peg trying to fit in a round hole.