Tom Rees will have a scan on his injured shoulder knowing he is battling to keep alive his hopes of a place on the Lions tour of South Africa this summer.

The England flanker was forced off during London Wasps' 36-18 win over Bristol yesterday amid fears that he may have damaged his shoulder joint.

Rees has recovered from knee ligament damage this season to push for a Lions place and his latest injury could not have come at a worse time as Ian McGeechan will announce his 35-man party for the three-Test tour tomorrow.

Even if Rees is given the all-clear he is still not guaranteed a call-up. For him to be in the squad the selectors would have to make David Wallace a No8 nominee to allow for another open side flanker.

The main casualty from that move would be Ryan Jones, the Wales captain who would then join England captain Steve Borthwick in failing to make the trip.

It is understood only four Wasps players are certainties to make the tour; Simon Shaw, Joe Worsely, Riki Flutey and Phil Vickery with Munster's Paul O'Connell to be named captain.

Danny Cipriani's improved form is not expected to earn him a tour place with England rival Toby Flood ready to edge ahead of James Hook, one of the many Welsh candidates being hampered by the Ospreys' fall from grace, if the Lions go with three outside halves. If they opt for just two, the tourists would have to use Flutey as a back-up No10 as Stephen Jones and Ronan O'Gara cannot be expected to be in all 10 match squads on tour.

There are around eight places that will go right to the wire, including world player of the year Shane Williams, whose defence is being seriously questioned by McGeechan and his fellow coaches. It may seem strange to penalise one of the few mercurial talents in British and Irish rugby because he is vulnerable to the high kick to the corner but the Lions know this will be a key weapon and that is why Delon Armitage will be considered for both full back and wing. England prop Andrew Sheridan is another whose tour place is under pressure with Ireland's Marcus Horan in the frame.

With so many of the Lions management either involved with Wasps - McGeechan and Shaun Edwards - or formerly at the club - Warren Gatland and Rob Howley -there were fears of bias but the omission of James Haskell will prove this is not the case.

McGeechan watched a two-try performance from young scrum-half Joe Simpson help beat Bristol and keep alive Wasps' Heineken Cup hopes yesterday.

The race for those Cup spots and the top four Premiership play-off positions is tight with second placed Harlequins and London Irish, in fourth, both on 61 points - five behind leaders Leicester who beat Saracens 16-13 yesterday. London Irish lost 21-17 at Northampton and Toby Booth, their director of rugby, will be hoping captain Bob Casey is ready to return from a bicep injury for the last game away at Worcester on Saturday.