Stevens replaced Armin Veh at Stuttgart earlier this week - just six months after leaving the club - and enjoyed a dream comeback at the Mage Solar Stadion on Friday.
Goals from Carlos Gruezo and Timo Werner, and a double from Martin Harnik, moved Stuttgart off the bottom of the table by ending their three-match winless run.
Both sides were wasteful in the early stages, but Harnik opened the scoring just after the half hour, the striker heading home from an Antonio Rudiger knock-down.
Freiburg's Vladimir Darida levelled with four minutes of the half to play, with his 25-yard shot arrowing past Sven Ulreich and into the bottom corner.
Stevens' words at half-time seemed to galvanise the visitors, though, and seven minutes after the break they were ahead, Gruezo collecting a loose ball on the edge of the area and firing home.
Stuttgart then extended their advantage on 68 minutes as Werner collected a pass from Moritz Leitner and coolly slotted the ball under the advancing Roman Burki.
Any hopes Freiburg had of getting back into the game suffered a severe blow when Stefan Mirovic was sent off for a foul on Harnik with 20 minutes to play.
And Stuttgart's win, which moves them level with Freiburg in the Bundesliga table, was confirmed shortly after when Harnik added a fourth, tapping Gotoku Sakai's cross-cum-shot home.
