Monaco ground out a 1-0 home win against Aston Villa in the Champions League on Tuesday, denying the Premier League side the chance to all but book their spot in the round of 16.
Wilfried Singo's early header was the difference between the teams as Villa tasted defeat for the first time in six outings in all competitions.
Monaco had only won two of their last 11 matches, including back-to-back defeats in the Champions League, but now have their eyes on securing progress to the knock-outs.
The defeat dropped Villa from fifth to seventh provisionally. They can qualify automatically for the last-16 with a top-eight finish.
"We started the Champions League not being favourites to finish in the top eight, and we still aren't. Tonight we are disappointed," said Villa manager Unai Emery.
Emery's side host 21st-placed Celtic in their final league phase match next week.
Villa and Monaco are among nine teams on 13 points, ahead of the rest of this week's matches, a pack headed by Arsenal in fourth place in the table with Monaco in ninth.
Monaco conclude their league phase campaign with a visit to Italian champions Inter Milan – also on 13 points ahead of a visit to Prague on Wednesday – knowing nothing but a win will do to avoid a play-off spot.
"We have one match remaining which will be very difficult. We are going to go to Milan next week with a lot of ambition and to win," said Singo.
Villa goalkeeper Emiliano Martinez's every touch was booed by the home support in the early stages – the crowd had not forgotten his role in Argentina's 2022 World Cup final victory over France.
To the delight of their fans, Monaco's opener came after the Argentinian parried Thilo Kehrer's header from a corner up into the air. Singo pounced to nod home from close range on eight minutes.
Martinez showed his class with a sprawling dive to claw away Maghnes Akliouche's whipped effort shortly afterwards.
'IMPORTANT WIN'
Villa came within inches of levelling in first-half added time following excellent build-up play by Emiliano Buendia, but Radoslaw Majecki got down quickly to deny Ollie Watkins.
At the start of the second period, Morgan Rogers flashed a strike narrowly wide, before Akliouche had a strike disallowed for offside.
Emery turned to Jhon Duran from the bench to give his side a spark, sending on the Colombian 11 minutes after the interval in place of winger Bailey.
With Watkins and Duran on the pitch together, Villa boasted a striking duo with 22 goals between in all competitions this term.
Rogers and Matty Cash combined to create Villa's next chance, the right-back dragging his effort across goal and wide on 69 minutes.
Monaco looked the more likely to score in the final 20 minutes.
Aleksandr Golovin rippled the side netting from a tight angle in the 88th minute.
Duran then attempted a bicycle-kick in the crowded box in the 92nd minute, but his ambitious effort flew well over the bar as Monaco held firm.
"It was an important win," said Monaco coach Adi Huetter. "I give compliments and praise to my team for how they fought."