Seahawks fans gave him the nicknames of "Dr. Dan" for his medical career, and "Mr. Third Down" for his knack of frequently picking up a first down for the team on third down when given the ball via run or pass. He ran for 123 yards on 27 carries for the Seahawks in a wild-card playoff win over the Los Angeles Raiders on December 22, 1984 in the Kingdome in Seattle. After a series of injuries in 1985, Doornink was released by the Seahawks in August 1986.[4][5]
In August 2021, Doornink was hospitalized for COVID-19. Although vaccinated, he has an autoimmune blood disorder which makes him more susceptible to complications. Doornink was placed on a ventilator and then removed from it when his breathing improved.[6] After being released from the hospital, he needed months of recovery.[7]