Champions League titleholders Paris Saint-Germain lost 2-1 at Sporting Lisbon on Tuesday to jeopardise their chances of a top eight finish and direct qualification for the last-16.
Luis Suarez scored twice for Sporting in the second half, sealing victory with a 90th-minute header after substitute Khvicha Kvaratskhelia had equalised for PSG.
Following victories for Real Madrid and Tottenham, PSG with 13 points have dropped to fifth place provisionally before Wednesday's matches – closely followed by Sporting.
Their home game against Newcastle in eight days will determine whether the Parisians avoid the two-legged playoff in February.
Despite being largely dominant PSG were unable to convert their early advantage into goals.
Lisbon striker Suarez ignited the home crowd with a clinical finish to beat Lucas Chevalier after 74 minutes.
A poorly cleared corner followed by an unfortunate deflection proved fatal to the hitherto impenetrable Parisian defense.
Kvaratskhelia levelled after 79 minutes but Suarez struck again late.