Dries Mertens scored his 121st goal for Napoli before being substituted against Barcelona on Tuesday.
Three English clubs and both Celtic and Rangers are hoping to secure places in the last 16 of the Europa League this week, while former European Cup winners Ajax and Inter Milan are bidding to qualify in adversity, for different reasons.
Chelsea must believe in a comeback against Bayern Munich, forward Olivier Giroud said.
Barcelona will be without two key players for the Champions League last-16 second leg against Napoli, but Quique Setien is unfazed.
After scoring four against Tottenham in October, Serge Gnabry continued his love affair with London with a brace against Chelsea.
Preston North End succumbed to West Brom on Tuesday, while promotion hopefuls Brentford and Bristol City lost on their travels.
Barcelona salvaged a 1-1 draw at Napoli on Tuesday, but Antoine Griezmann expects more at Camp Nou.
Chelsea manager Frank Lampard admitted a 3-0 thrashing at home to Bayern Munich in the first leg of their Champions League last 16 tie was a reality check for how far behind the European elite the Blues now find themselves.
Bayern Munich swept Chelsea aside with ease as two quickfire goals from Serge Gnabry and Robert Lewandowski's long-awaited strike in the knockout stages of the Champions League gave the Germans a commanding 3-0 last 16, first leg win on the road.