Hamburg earned a second chance at securing their Bundesliga status with a 2-0 win over Schalke.
Liverpool give U21s more game time than Premier League rivals but top flight lags behind Europe.
Stuttgart climbed off the foot of the Bundesliga and leap-frogged Hamburg in the standings with a 2-1 win.
Hamburg defended their place above Freiburg in the Bundesliga thanks to a last-gasp Gojko Kacar header.
A late Gojko Kacar goal lifted Hamburg out of the bottom three with a 2-1 victory at Mainz.
Hamburg picked up their first win since early February by beating Augsburg 3-2.