The Warriors' dismal Christmas period - home defeats against London Irish and Harlequins - has cut them nine points adrift of 11th-placed Northampton, who they tackle at Franklin's Gardens on Monday.
After the Saints clash, Worcester's 10 remaining league games include trips to top-five clubs Bristol, Leicester, Wasps and Gloucester, suggesting that time is running out during a prolonged survival fight.
Brain said: "I suppose we will be totally written off. The only crumb of comfort is that we've lost two games over Christmas, both of which we could quite easily have won.
"We are at the bottom, so over the first 11 games, we have been the worst team. But I can say that we're not losing games by much, and we've got to make sure that we turn those margins round.
"The test is what really happens in the next few weeks. We now know that, as a team, we have a clear choice - we can either fragment or stick together.
"It would be a shame if we fragmented. We are capable of winning any game, and we want the next five matches to be positive."
Worcester have already lost to Northampton in the Premiership this season, while Saints' last home game produced a resilient 8-6 success against Wasps.
Wasps, well positioned in the title play-off zone, welcome back number eight Lawrence Dallaglio against Recreation Ground hosts Bath on Monday. Dallaglio also regains the captaincy from rested fly-half Alex King.
Rugby director Ian McGeechan said: "We are trying to look after the players and keep them fresh during this intense period of the season.
"We have been relatively lucky with injuries, and the depth of the squad and keen competition for places among the players allows us to rotate the team following our physical encounter with Gloucester on Boxing Day."
Bath go into battle with England forwards Lee Mears and Danny Grewcock on duty, despite them both being cited for alleged stamping incidents and facing Rugby Football Union disciplinary hearings in Bristol next Thursday.
London Irish, unbeaten in their last three Premiership outings, make the trip to Gloucester with Exiles rugby director Brian Smith still enthused by his team's thrilling Boxing Day success against Leicester.
Smith said: "We have to commend all the guys for the way they played against Leicester. Our pack gave what was their most complete performance of the season, to date.
"It has been another short turnaround for the trip to Gloucester, but we are in reasonably good shape with only a few niggles that will hopefully clear up before Monday, when another big squad performance will be required."
Premiership form team Saracens, whose win against Northampton last time out took them fourth, hand former Leicester academy pupil Tim Taylor his club debut in Monday's appointment with the Tigers at Welford Road.
Taylor replaces rested fly-half Glen Jackson, and Saracens boss Alan Gaffney is confident he will relish the occasion after arriving in the Premiership following a playing stint in New Zealand.
Gaffney said: "You could argue that this is throwing him in at the deep end, but he is a talented player with experience of the (New Zealand) National Provincial Championship, and he came to us highly recommended.
"He is a pretty cool customer, so he will be looking forward to running out against Leicester and showing us what he can do."
Leicester, frustrated by their defeat against Irish, retain just three players from that Madejski Stadium encounter in full-back Geordan Murphy, wing Alesana Tuilagi and lock Ben Kay.
Tigers head coach Pat Howard said: "Sixteen points from four games (over Christmas and new year) is still attainable, and we will aim for that.
"The London Irish result was disappointing because we thought we had a genuine shot at four wins in this period."
Elsewhere on Monday, champions Sale Sharks will hope to halt their slide by recording just a second league win in six league outings when leaders Bristol arrive at Edgeley Park.
But Sharks coach Kingsley Jones acknowledged: "Bristol are a good side, top of the league on merit. They have plenty of experienced players and are very difficult to play against."
Bristol are without England scrum-half Shaun Perry due to a rib injury, but their problems pale into insignificance when compared with a Sale casualty list that includes Charlie Hodgson, Jason White, Andrew Sheridan, Chris Jones, Mark Cueto and Lee Thomas.
Harlequins have lost scrum-half Andy Gomarsall and prop Ceri Jones to injuries ahead of hosting Newcastle on Monday, with Falcons keen to avenge a 14-3 home defeat against the Londoners in mid-November.