CHENNAI (AFP) - England captain Andrew Strauss and off-spinner Swann are in doubt for the key World Cup clash against the West Indies after missing training on Tuesday. An England spokesman said both players were suffering from stomach problems. Meanwhile struggling fast bowler James Anderson was seen receiving treatment for a small problem with his right shoulder during training but the team spokesman said he remained available for selection. England must beat the West Indies at Chennai's Chidambaram Stadium on Thursday to have a chance of qualifying for the quarter-finals -- and even then they will need other results to go their way. Defeat would see England, already beaten by Ireland and Bangladesh, crash out of the World Cup before the knockout phase. England head into their final Group B match against the West Indies on Thursday knowing defeat will send them crashing out of the World Cup. Even victory may not be enough for Andrew Strauss's men to go through to the knockout stages, with England having to rely on other results going their way. England's preparations suffered a setback when skipper Strauss and lead spinner Graeme Swann both missed training Tuesday through illness while strike fast bowler James Anderson received treatment for a shoulder niggle. A see-saw tournament for England has seen them lose to Ireland and Bangladesh yet tie with India and beat a highly fancied South Africa side. Significantly, that win over the Proteas came at Chennai's Chidambaram Stadium, where England held their nerve on a sharply turning pitch to win a low-scoring thriller by six runs. Now they hope Swann is fully fit to again put the squeeze on the batsmen in a match that is not quite as decisive for the West Indies, who return to the Chidambaram three days later for a group finale against India. "It does give things a certain amount of clarity," said Swann, all but unplayable at times while taking one for 29 against South Africa. "If we win four games, we win the World Cup which is very simple. If we'd won our first four games it would have been a much nicer position to be in but there's no point in looking back. It all comes down to Thursday." Swann, who in his first over in Test cricket took two wickets against India in Chennai in 2008, added: However, he warned: "The West Indies have got Sulieman Benn, who is a fine spin bowler." The West Indies have two big-hitting batsmen in opener Chris Gayle and the in-form Kieron Pollard who can change the momentum of a match in a short space of time. Pollard hammered 94 off just 55 balls as the West Indies beat Ireland by 44 runs last time out and it was an innings the all-rounder hopes has rid him of the tag of being 'just' a T20 cricketer. "What's been said about me being a 20-over specialist, that's just history for me now," Pollard said.