David Luiz missed a penalty kick for Chelsea, 1 draw Tuesday at Cristal Arena.
Ramires scored inside 30 minutes for Chelsea, and then a handball just inside the area set up a penalty for Luiz, but the Brazilian defender was denied off his attempt toward the left post, and the Blues later allowed the tying goal.
Chelsea remained atop Group E after four matches, but left all three opponents in the running for a berth in the knockout stages entering the last two rounds of group play.
Bayer Leverkusen is two points back in second, Valencia is three back in third and Genk is hanging on with two points in fourth.
Chelsea got off to a good start when Fernando Torres and Ramires worked a fast passing sequence, with the Spaniard playing the final pass into the area for the Brazilian Ramires to slot through goalie Laszlo Koteles' legs in the 26th.
Raul Meireles hit the crossbar later in the half, and Florent Malouda's cross in the 39th bounced off the hand of Genk's Khaleem Hyland for a penalty. But Luiz was denied by Koteles, and Genk responded with the tying goal after half.
Having missed a solid chance earlier in the half, Genk found the tying goal on 61 minutes when Fabien Camus played Vossen into the area and he scored to the left post from the middle of the area.
Malouda nearly secured three points for Chelsea in the 90th, but his floating shot was cleared off the line by a Genk defender, who kicked the ball off his own teammate just off the goal line, but it deflected just wide of the post.
Barcelona 3, Viktoria Plzen 0
Prague,Czech Republic - Lionel Messi had a hat trick to take over the scoring lead in the Champions League, and Barcelona rolled to a 4-0 win over Viktoria Plzen on Tuesday at Synot Tip Arena to clinch a knockout berth.
Marian Cisovsky was sent off after 22 minutes for Plzen for a foul on Messi in the area, and the reigning two-time world player of the year followed in the 24th with the opening goal from the penalty spot.
Messi added his second of the match just before half, as he took a pass from Adriano and scored to the lower-right corner. Cesc Fabregas added a third goal on 72 minutes for Barca, and Messi completed his hat trick with a goal to the bottom left in stoppage time. Messi has five goals in four CL matches.
Barcelona moved to the top of Group H on 10 points, has a two-point cushion on AC Milan, and cannot be caught by either Plzen or BATE.
BATE 1, AC Milan 1
Minsk, Belarus - Renan Bressan converted a penalty kick 10 minutes after half, and BATE held AC Milan to a 1-1 tie Tuesday at the Stadion Dynama for just its second point in Group H of the Champions League, although the Italians sealed advancement.
Zlatan Ibrahimovic scored his third goal of the group stage in the 22nd minute as Milan grabbed the early lead, but the side from Belarus pulled even off the penalty to secure its second draw.
BATE tied Viktoria Plzen in its first group match, but lost its last two games to Barcelona and AC Milan by combined scores of 7-0. AC Milan has two wins and two draws from four games and, after Barcelona beat Viktoria Plzen, secured a berth in the last 16.
Only BATE can catch Milan on points, but the Italians won the series in group play because they won the first leg at the San Siro.
APOEL 2, FC Porto 1
Nicosia, Cyprus - Gustavo Manduca scored in the 90th minute, just following a disputed penalty from Hulk tied the match, and APOEL edged FC Porto 2-1 at GSP Stadium to remain atop Group G of the Champions League.
The Cyprus club has been one of the surprises of the tournament so far, and is unbeaten after four matches and atop the group with eight points. Zenit is one point back in second, while Porto is four off the pace in third.
Ailton Almeida gave APOEL the lead 3 minutes before half, but James Rodriguez drew a penalty with little contact in the closing minutes of normal time, and Hulk converted to tie the match.
APOEL secured a deserved victory when Konstantinos Charalambides' cross found Manduca, who finished to the bottom-left corner in extra time.
Valencia 3, Bayer Leverkusen 1
Valencia, Spain - Jonas notched the second-fastest goal in Champions League history just 12 seconds into the match, and Roberto Soldado and Adil Rami had goals in the second half, as Valencia beat Bayer Leverkusen 3-1 in Group E of the Champions League on Tuesday.
Jonas latched onto a defensive mistake by Leverkusen off the opening kickoff, then slotted inside the left post from outside the area to come within just 2 seconds of the fastest goal in the competition's history.
Stefan Kiessling pulled a goal back for Leverkusen in the first half, but the German side failed to hold on as Valencia moved within one point for second in the group. Chelsea leads the group, and Genk is also still alive.
Zenit 1, Shakhtar Donetsk 0
Saint Petersburg, Russia - Nicolas Lombaerts scored in first-half injury time, and Zenit beat Shakhtar Donetsk 1-0 on Tuesday at Petrovsky Stadium to improve its chances of advancing from Group G in the Champions League.
Zenit won its second match of the stage, and has seven points from four games. The Russian side is unbeaten in three straight group matches since a defeat to APOEL in Cyprus to kick off the stage.
Shakhtar Donetsk is winless after four games with just two ties and has almost no shot to escape the group stage. Third place and a spot in the Europa League is still possible.
Arsenal 0, Marseille 0
London, England - Arsenal settled for a 0-0 draw against Marseille on Tuesday at the Emirates Stadium, but retained its lead atop Group F of the Champions League.
Arsenal tied for the second time through four matches, but on the strength of twins in its other fixtures, has a one-point lead over Marseille ahead of the last two group matches.
Arsenal has advanced to the knockout stage 11 straight times, and will try to clinch a 12th straight when Borussia Dortmund visits on matchday 5 on Nov. 23. Marseille can also clinch that day if Arsenal wins and it beats Olympiacos.
Borussia Dortmund 1, Olympiacos 0
Dortmund, Germany - Kevin Grosskreutz scored in the 7th minute and Borussia Dortmund revived its Champions League hopes with a 1-0 win over Olympiacos on Tuesday at Signal Iduna Park.
Dortmund was winless after three matches, but used the win to move into third and within four points of Group F leader Arsenal. Marseille is three points in front in second, while Olympiacos is one point behind Dortmund.
Olympiacos defeated Dortmund in the last round of matches.