Pepe Mel's side are just three points above the relegation zone and have played two games more than 18th-placed Sunderland.
That leaves The Hawthorns outfit perilously close to losing their top-flight status just one season on from their highest finish in more than 30 years.
A top-eight spot last time out appeared to underline how well West Brom had settled among English football's elite, but this campaign has seen Steve Clarke depart and Mel struggle to reverse the losing trend, with his charges on 28 points.
However, Foster believes that a relatively low points tally might be enough to stay up this term and he recognises that each game is vitally important, starting with Saturday's visit of second-bottom Cardiff City.
"I think maybe 36 or 37 points will probably do it this season," he told the club's official website. "It's really tight down there, so first things first we need to get three points from the Cardiff game.
"Then our run-in isn't as bad as some other teams – we've got Arsenal away, Tottenham at home and Man City away but the rest are all teams around us so we need to remain positive.
"Each game is a monster game in all honesty."
West Brom were beaten 2-0 at Hull City on Saturday, with former fans' favourite Shane Long winning a controversial first-half penalty and then scoring himself seven minutes later.
The spot-kick call is one of several debatable decisions to have gone against Foster's side this season, but he is keen to look ahead.
"We've got to put Hull behind us now, Cardiff is another six-pointer," he added.
"If you look at the Swansea game (Mel's sole win so far) we did so well there, we just need to take a bit of confidence from that really.
"I thought we did well up until the penalty on Saturday, the penalty was a game changer. So there are some positives to take."
