Lens won its 10th straight home game in the French league on Saturday, defeating struggling Auxerre 1-0.
Przemyslaw Frankowski of Poland scored a penalty kick in the 59th minute with a powerful strike past goalkeeper Benoît Costil, who guessed correctly.
Auxerre finished with 10 players after defender Isaak Touré was sent off for a second yellow card for fouling forward Florian Sotoca midway through the second half.
Lens, which has won all of its home games this season, has moved three points behind leader Paris Saint-Germain.
Lens extended its unbeaten league run to nine games but remains two points behind third-placed Marseille after beating Lorient 3-1 at home for their sixth straight league victory.
Second place guarantees an automatic spot in next season’s Champions League, while third place requires a playoff round entry.
Terem Moffi, the danger man for Lorient, scored again in the 29th minute with a superb volley from a corner. It was the Nigerian striker’s 12th league goal, putting him one ahead of PSG’s Neymar and one behind PSG’s top scorer, Kylian Mbappé.
Marseille has been resilient this season under coach Igor Tudor, and they responded 10 minutes later when defender Sead Kolasinac headed in a cross from Turkey winger Cengiz Ünder.
Alexis Sanchez, a veteran Chile striker, put Marseille ahead in the 53rd minute with a powerful finish from Kolasinac’s deflected cross, and France midfielder Jordan Veretout’s shot following a long ball made it 3-1 six minutes later.
Strasbourg also moved out of the relegation zone with a 2-1 win over Lyon.
In the 28th minute, midfielder Jean-Eudes Aholou volleyed in from a corner, and striker Habib Diallo doubled Strasbourg’s lead four minutes later.