Trainer Leonard Powell saddles Canadian Exchange (#3, ML 3-1) in Thursday's first race at Del Mar, a six-furlong maiden claimer. Since Jan., 1, 2014, Powell is winning at a 30 percent clip when saddling a horse switching from turf to dirt, for a return on investment of $3.78. Check out the Positive ROI report as part of DRF Plus. Sign up for DRF Plus here.