Stuttgart suffered a first home defeat in more than a year as second-half goals from Ademola Lookman and Nicolo Zaniolo gave Atalanta a 2-0 win in Germany.
Not since a 3-2 Bundesliga reverse against Hoffenheim in late October 2023 had Stuttgart been beaten at Neckarstadion, but that run was ended in the Champions League on Wednesday.
Atalanta arrived in Stuttgart undefeated in eight and having stunned Serie A leaders Napoli away from home at the weekend, yet this latest upset only became possible with the half-time introduction of Charles De Ketelaere.
He quickly created the breakthrough goal for Lookman after beating two defenders, and the German side faced an uphill struggle thereafter.
They could not come up with an equaliser and instead conceded a clinching second goal when Zaniolo pounced on a defensive error and slipped the ball past Alexander Nubel.
As victory took Atalanta up to ninth on eight points, Stuttgart fell out of the play-off places with four points at the halfway stage of the league phase.
Data Debrief: Home form not reflected in Europe
Despite Stuttgart's previous dominance at home, their European record at Neckarstadion continues to leave a lot to be desired.
Having drawn with Sparta Prague earlier in this campaign, Stuttgart are winless in eight home matches in major European competition. In fact, they are without a home Champions League goal since 2007.
The joy of an away win against Juventus will count for little if Sebastian Hoeness' side cannot turn their fortunes around at home, where in domestic competition they have been so strong.
Meanwhile, seven of Atalanta's 10 Champions League wins have now come on the road.
