The Oakland Athletics have signed supplemental first-round draft pick Daniel Robertson, according to Jim Callis Baseball America. Robertson received Major League Baseball's recommended slot signing bonus for the 34th overall selection, which is valued at $1.5 million.

Here's Callis' take on the California High School third baseman:

"A product of Upland (Calif.) HS who had committed to UCLA, Robertson has a quality bat with a chance for average to plus power. He also has good hands and arm strength, helping him profile as a valuable defender as well."

The Athletics really surprised some with their draft this year. They usually stick to college players, but took three high school players with their top three draft picks and five of their top seven.

According to our signings tracker, the A's have now signed their two top draft picks, the other being high school product Addison Russell, and three of their top four draft picks. The one that remains unsigned is Matt Olson.