London: Chelsea's Champions League future hangs in the balance with the Premier League side needing to beat Valencia on Tuesday to guarantee their place in the knockout stages for a ninth successive season.

A Valencia victory would put the Spaniards safely through from Group E and pile further pressure on Chelsea manager Andre Villas-Boas who has come under intense scrutiny in recent weeks.

The Portuguese's stuttering side have lost five of their last 10 matches in all competitions as their normally solid defence has become increasingly erratic and an expensively assembled frontline has failed to fire.

Villas-Boas's former team Porto, twice European champions, will also suffer an early exit from the competition if they fail to beat Zenit St Petersburg in Group G.

Despite topping their domestic table, Porto coach Vitor Pereira is also under pressure with his team struggling to reproduce the rampant attacking football that helped them win the Europa League as well as a domestic double last season.

Olympique Marseille travel to Borussia Dortmund in Group F needing to beat the German side to reach the next round.

Should they slip up, third-place Olympiakos Piraeus, who face group winners Arsenal, are in pole position to snatch the final qualifying spot while Dortmund retain an outside chance of going through.

With Barcelona and AC Milan qualified from Group H, the only issue to play for is who out of Czech side Viktoria Plzen and BATE Borisov of Belarus finish third and qualify for the Europa League.