Zenit St Petersburg's title ambitions face a stiff test on Saturday when Andre Villas-Boas' Russian league leaders take on reigning champions CSKA Moscow.
Zenit top the Premiership table with 29 points from 11 matches, four points clear of CSKA, with FC Krasnodar in third on 21 points.
Against the Red Army side Zenit are hoping to bounce back after crashing out of the Russian Cup Wednesday with a 3-2 extra-time defeat to lowly Arsenal Tula.
"It's a big shock for us," former Chelsea and Tottenham manager Villas-Boas said.
"With 10 minutes to go we had everything we needed to go through but we managed to lose control on the game.
"Now we have a big game coming up and it's a completely different story because it is the championship and we are still leading there.
"We need to get our concentration back, but without forgetting this one. It's a good example to take in to make sure that the games like this never happen again."
On Saturday Villas-Boas will be able to field a full-strength squad, while CSKA are still without  Brazilian Vitinho and the Swede Rasmus Elm, while Ivory Coast sharpshooter Seydou Doumbia has still to hit top form.
CSKA, who advanced into the Russian Cup's last eight with a confident 2-0 win over city rivals Torpedo, are aiming to narrow the gap to the leders Zenit in their head-to-head clash.
"We're satisfied both with the result of our cup match and the way we've achieved it," CSKA head coach Leonid Slutsky said.
"Some of our team's leaders received a rest and were not playing on Wednesday. Now I expect them to perform at their top against Zenit.
"We all understand the great importance of this match and are hoping to achieve a positive result on Saturday."
Meanwhile FC Krasnodar, who beat Terek Grozny 2-0 a week ago to go third, have a decent chance to claim all three points at Mordovia Saransk, who have lost their last two Premiership matches by the same 5-0 scoreline.
On Thursday Krasnodar, who were without their two key midfielders Vladimir Bystrov and Marat Izmailov, were knocked out of the Cup 3-1 by Samara.
"The match exposed our weaknesses," said Kranodar manager Oleg Kononov.
"We must draw conclusions from this defeat to avoid it in the future. The upcoming match with Mordovia will show whether we're capable of doing that."
Fixtures (all times GMT)
Friday
Rostov v Ural Yekaterinburg (1600)
Saturday
CSKA Moscow v Zenit St Petersburg (1300)
Sunday
Lokomotiv Moscow v Dynamo Moscow (1030), Mordovia Saransk v FC Krasnodar (1330), Kuban Krasnodar v Spartak Moscow (1600)
Monday
Torpedo Moscow v Arsenal Tula (1100), Rubin Kazan v Amkar Perm (1330), Terek Grozny v Ufa (1600)
Source: AFP