|A missed penalty by David Luiz did not help Chelsea's bad week as they were held to a 1-1 draw at Genk [GALLO/GETTY]
Lionel Messi's hat trick helped Barcelona stroll into the European Champions League knockout phase with a 4-0 rout of Viktoria Plzen, and AC Milan also qualified early from Group H with a 1-1 draw at BATE Borisov on Tuesday.
Messi scored his 200th Barcelona goal from the penalty spot, netted again for the champions on the stroke of halftime after completing a one-two with Adriano and rounded off the victory in stoppage time following Cesc Fabregas' header.
Second-place Milan qualified despite Zlatan Ibrahimovic's goal being cancelled out by Renan Bressan's penalty kick for BATE.
Group F leaders Arsenal missed out on qualifying with two games to spare after drawing 0-0 with Marseille.
Borussia Dortmund climbed off bottom place with a 1-0 victory over Olympiakos.
Chelsea extended their Group E lead to two points despite being held 1-1 at Genk as second-place Bayer Leverkusen lost 3-1 at Valencia.
APOEL retained their surprise lead of Group G by beating FC Porto 2-1, staying a point ahead of Zenit St. Petersburg, who beat Shakhtar Donetsk 1-0.
Barcelona's status as Europe's most formidable force remains unchallenged, having outscored opponents 26-0 in their last nine matches.
The first in Prague came after 24 minutes when Messi slotted a penalty into the bottom left of the net after being brought down by Marian Cisovsky, who was sent off.
The second was more clinical, dispatching the ball past goalkeeper Roman Pavlik after Adriano had helped him finish another flowing move by the Spanish champions.
Messi's fourth hat trick of the season - taking his tally to 22 goals in 18 goals - was completed with almost the final touch of the game, after being played in by Gerard Pique's neat backheel.
Fabregas' downward header from Isaac Cuenca's cross came in the 72nd after being left unguarded close to goal.
Barcelona are two points ahead of Milan, who escaped Belarus with a draw after a sloppy performance.
Ibrahimovic put Milan ahead in the 20th, striking the ball into the bottom corner of the net after latching onto Robinho's cross. But Ignazio Abate gave away a penalty, which Bressan converted 10 minutes into the second half.
"We made a lot of mistakes, and when you do that then it can happen that you concede a goal or penalty,'' Milan coach Massimiliano Allegri said.
"It's normal that you have to be more clinical in finishing a game off, but we didn't do that.''