In the $8,000 maiden claiming event, Little G Man fell after clipping heels with Latin nearing the quarter pole. Ward Brooks and Knoblock then tripped over Little G Man while Irish Yodeler lost his rider trying to avoid the accident. Knoblock broke down in the spill. Latin did not fall and finished fourth.
Lopez, who rode Little G Man, suffered a rib fracture and a bad bruise on his right thigh. Martinez, who rode Knoblock, has a broken rib and a minor back fracture. Both riders were to be released in the evening, according to a track spokesman.
Jockey Jorge Ayarza, who picked up the mount on Irish Yodeler, suffered bruised shoulders but remained at the track to ride Fear the Storm in race nine.
Jockey Doug Portillo, who had no remaining mounts after riding Ward Brooks in race five, had bruises on his right forehead.
Knoblock, who fractured his left front knee, and Little G Man, who sustained major injuries when he fell, both had to be euthanized. Ward Brooks and Irish Yodeler chased the field home and came out of the spill unscathed.