The Athletics are calling up Gage Jump, one of the best left-handed pitching prospects in baseball, sources told ESPN's Jeff Passan on Monday.

The No. 2 prospect in the A's system, Jump, 23, runs his fastball up to 97 mph and has struck out 56 in 38 innings at Triple-A Las Vegas.

The Athletics (27-27) are atop the American League West standings, but their pitching staff ranks in the bottom third in the majors in strikeout rate.