Matt Barnes is really, really good. While he was charting pitches yesterday, Barnes got to talking about Jackie Bradley Jr. as a centerfielder. Bradley's instincts in center are off-the-charts, so he's able to be a great defensive centerfielder despite his average speed. Barnes, in a similar sense, has great instincts on the mound. The difference with Barnes is that he has elite stuff to go with it.
Barnes uses a fastball that sits 94-96 and touches 97 and features plenty of movement. His curveball, which you can see a couple times above, sits in the mid 70s and and features plenty of late break. Most of the time it had 12-6 action and looked like a plus pitch. The UConn product also showed a high 80s changeup that played up because of his fastball velocity and might end up an average pitch.
Barnes showed plenty of pitchability, mixing his pitches well and missing bats. Many Sally League hitters just don't have the bat speed to hit that type of velocity, and often can't track breaking balls into their bats, so Barnes's success could be a product of poor competition. That could change by the time he takes the mound again though, as he is rumored to be headed to High-A Salem for his next start.