Moscow (AFP) - Andre Villas-Boas's Russian league leaders Zenit St Petersburg face their first serious test this season as they look to defend a 100 percent record against Lokomotiv Moscow on Sunday.
Last season's runners-up Zenit have won all five of their Premiership encounters this season to remain the league's only side with an unblemished record.
But all of their wins were achieved in matches with the league's underdogs and newly-promoted clubs. The clash with two-time former champions Lokomotiv will be the season's first serious test for the Saint Petersburg outfit.
When the two teams last met in Moscow in May the match ended in a 1-1 draw. That points loss helped cost Zenit the domestic title as they finished just one point behind CSKA Moscow.
Zenit go into the Sunday's encounter on the back of a morale-boosting 3-0 win over Belgian club Standard Liege, which opened the door into the Champions League group stage for the Russian club.
However, several Zenit players -- including Brazilian star Hulk -- have already suffered minor injuries through tiredness, while the match with Lokomotiv will be their ninth outing in August.
"We're happy to go through to the Champions League group stage," said Villas-Boas, the former Porto, Chelsea and Tottenham coach.
"But we have had a very busy schedule in August with plenty of flights. It wasn't easy to survive it as we had to pay a lot of attention to our footballers' recovery.
"But now before Lokomotiv, we have some more time so I am sure that we'll be ready to play at out best on Sunday."
Second-placed Spartak Moscow, who beat Ufa 2-1 at Perm a week ago, face hosts Amkar on the same synthetic pitch of the Perm Zvezda arena.
Russia's most successful club, who have won four of their five Premiership matches this season while Amkar are second from bottom with just one point so far.
Spartak's Swiss coach Murat Yakin, who took over the former nine-time champions during the summer break, said he was happy with the way things have been going in Moscow.
"My team, and me personally, are experiencing a very intense and thrilling season and I'm very happy to be a part of it," he said. "I'm really excited with the decision to continue my career in Russia."
Another Moscow side, Dynamo, who share second spot with Spartak, will also have to pass a tough test to their title ambitions at FC Krasnodar, who thrashed Spartak 4-0 earlier this month.
Dynamo coach Stanislav Cherchesov said that his team are beginning to solve the enigma of fitting French playmaker Mathieu Valbuena into their system.
"We experienced certain difficulties in mutual understanding and the team's coordination after signing Valbuena, who didn't go through our pre-season training camp," he said.
"But ahead of the match with Ural, Valbuena understood our demands and the team's needs. As a result he played compactly and was very useful in our last encounter. I'd say he is rapidly becoming an integral member of our team."
Reigning champions CSKA, still without a host of first-team players due to injuries, will take on 10th-placed Rostov on Sunday.
Mordovia Saransk v Torpedo Moscow, Amkar Perm v Spartak Moscow, Arsenal Tula v Kuban Krasnodar
CSKA Moscow v Rostov, Rubin Kazan v Ufa, Lokomotiv Moscow v Zenit St Petersburg, FC Krasnodar v Dynamo Moscow