Racing and Penarol dropped points for the first time this Uruguayan Primera Division season after both drew matchday four.
Mauricio Larriera's Racing was held to a 1-1 draw at home to Juventud, but still remains top of the table.
Penarol failed to capitalise as it drew at Defensor Sporting, while El Tanque Sisley joined the top two on 10 points.
Damian Malrechauffe had put Penarol on track in Montevideo, opening the scoring in the 28th minute.
But the 11th-placed visitor levelled just 10 minutes later through Gaston Puerari.
Penarol sits second and is still yet to concede this season, playing out a scoreless draw at Defensor Sporting.
Those results helped El Tanque Sisley, who moved onto 10 points and is the only other undefeated team, after a 2-0 win over Rentistas.
Felipe Rodriguez scored early on and Yoel Burgueno sealed the win with minutes remaining.
River Plate suffered its second loss in four league matches, beaten 3-1 by Nacional in their derby clash.
Diego Arismendi and Gonzalo Porras were on the scoresheet in the opening 32 minutes for Nacional.
Santiago Garcia pulled a goal back before Ivan Alonso restored Nacional's two-goal lead with his sixth goal of the campaign.
Claudio Herrera saw red in the 76th minute.
Cerro remains the only point-less team in the league, thrashed 4-0 at Tacuarembo, while Matias Castro's brace helped Danubio thrash Rampla Juniors 5-0.
Atenas claimed its first win of the campaign as Santiago Barboza's 70th-minute penalty saw it past Wanderers 1-0.
Canadian forward Lucas Cavallini's brace was not enough for Fenix, who drew 2-2 at Sud America.