Anybody who thought the two draws with which Zenit St Petersburg began the third – and final – part of this marathon Russian season might signal a dip in form, opening the possibility of a realistic title challenge, was rapidly disabused on Friday. Dynamo Moscow were third in the table and had lost only twice in 17 home games this season; they seemed a genuine threat. If they could even have held Zenit to a draw, CSKA could have closed to within four points with a win in the Moscow derby against Spartak. CSKA fulfilled their part, winning 2-1, but Zenit were imperious, winning 5-1, keeping the gap at six points and, by the manner in which they did so, emphasising just how far they are ahead of every other team in Russia.

The injury to Danny, such a hub of their play as a playmaker drifting in from the left, might have derailed them, but the loan signing of Andrey Arshavin has plugged that gap. He hasn't completed any of the three games he's started for Zenit since his return from Arsenal, but his fitness is improving and, after managing only 55 minutes in his first game, he went up to 66 in his second and 71 against Dynamo. It was his assist, darting in from the left and rolling a precise pass for the ageless Sergei Semak that brought the third goal and, at that stage, he was, the match report in Sovetsky Sport noted, "the hardest-working and more dangerous player on the field".

"We displayed high-quality football, combining up nicely with each other," Arshavin said. "We took our chances well and gave the travelling fans something really special. Everything was good except the pitch which was difficult for both teams. Dynamo started the game badly and made a few mistakes and as a result we punished them."

The first two goals came from atrocious defensive errors and that, perhaps, offers the only hope for Zenit's rivals: Dynamo were two down within 15 minutes and left themselves so open as they chased the game that Zenit were able to slice through them. Alexander Kerzhakov scored two more to take his tally for the season to 20 but, inevitably, it was Arshavin who attracted most of the post-match attention.

"He looks better and better with each match," said the Zenit coach, Luciano Spalletti. "I can't judge his form. He worked hard in training at Arsenal but he lacked match practice and, as a consequence, playing shape. But he'll continue to improve."

A lack of match practice may well have been true towards the end of Arshavin's time at Arsenal – he managed just 84 minutes of playing time between the FA Cup tie against Leeds on 4 January and the end of February – but the question really is what happened before that. Arshavin is far from being back to the sort of form he showed in 2008, but he's an awful lot nearer now than he was before rejoining Zenit. A return home seems to have inspired him; perhaps his problem in his latter months in London was simply homesickness.

It's an affliction that seems particularly common among Russians: Yegor Titov has said he used to feel sick as soon as the wheels left the tarmac at Domodedovo, and in Among The Russians Colin Thubron is struck by the depth of feeling Russians have for home, how the notion of Mother Russia is so strong it almost ceases to be a metaphor.

Arshavin himself is very much a child of St Petersburg; he even met his wife on Nevsky Prospekt. He's been heavily criticised by the Russian media for his recent performances for the national team, of which he is the captain, but it may be he is playing himself into form for Euro 2012.

The other issue, at least from an English point of view, concerns Spalletti, who has been mentioned in connection with the Chelsea job. Roman Abramovich, of course, will be aware of his achievements, but the Italian extended his contract to 2015 last month. It may be that it is a defensive move by Zenit designed to ensure they receive the best compensation possible but there has been absolutely no evidence of any sort of formal or informal approach by Chelsea.

Elsewhere, the Ivory Coast forward Seydou Doumbia scored his 26th goal in 33 games as CSKA won at Spartak to stay only six points adrift, but for them the battle really seems to be for the runners-up spot and the second Champions League qualifying place. They have stuttered badly of late, winning only one of 10 games in all competitions before the derby success, and they may give the pursuers hope.

Lokomotiv are four points back and unbeaten in the league since the winter break. They went third on Sunday with a 1-0 win over Anzhi – a game in which a banana was allegedly thrown at Christopher Samba. Guus Hiddink's appointment at the Makhachkala club has yielded four points in three games – and only one goal – and they lie seventh, eight points behind CSKA.

Champions League qualification is possible, with the top half of the league playing each other twice in this odd addendum to the season (brought about by the switch to an autumn-spring calendar), but it would require them to go on a superb run in the nine games that remain and their performances over the past fortnight have done little to suggest that is likely. The first task for them, though, is to make sure they finish in the top five and so secure Europa League qualification.