United, who beat CSKA Moscow 2-1 on Tuesday to reach the Champions League knockout rounds for the first time since 2013-14, face Guardiola's Manchester City on Sunday seeking to cut their eight-point lead in the Premier League.
Robert Lewandowski opened the scoring and Corentin Tolisso struck twice as Bayern Munich fell just short of topping Group B with a 3-1 win over Paris Saint-Germain at the Allianz Arena. In fact no side from the same country can play another at this stage.
Group H runners-up Real Madrid notched 17 as Cristiano Ronaldo made history by becoming the first player to score in all six first-phase games, while Harry Kane hit six for the section's winners Tottenham.
Juventus: Victory over Olympiakos will guarantee their place in the last 16. Despite a fifth loss in six group games, they limp into the Europa League in the new year.
United now have somebody capable of both stretching back fours with selfless runs and producing clever flick ons to set other players free - the latter serving as an avenue for their second goal against the Russian side - and their entire attacking approach feels more fluid as a result.
"We had to play him in two consecutive matches in three days [against] Watford and Arsenal and by our point of view he really needs the rest, so he's not even an option".
Tottenham: Basel (20), Bayern Munich (4), Juventus (5), Seville (7), Shakhtar Donetsk (16) or Porto (12).
Anything else you need to know? Diego Simeone's team will drop down into the Europa League knockout stages. The PSG forward breezes past David Alaba with ease and hits a low shot which is saved by Sven Ulreich.
Atlético Madrid have been knocked out of the Champions League in the group stages for the first time since the 2009-10 season.