Glen Jackson insists Saracens have not given up on the race for the Premiership play-offs but warned anything less than a win at leaders Gloucester tomorrow (Saturday) will spell the end of their faltering challenge.

The Men in Black return to Kingsholm for the first time since they were torn apart 50-9 by the rampant Cherry & Whites in the play-off semi final almost a year ago, and know another defeat there will reduce their one-time triple assault for silverware to just one.

However Jackson, who scored all his sides' points on that ill-fated afternoon, is in confident mood after helping chart Sarries' path into the Heineken Cup semi finals at the expense of fallible Welsh region, Ospreys.

Has the enormity of the 19-10 victory sank in yet? "It's had to really because we've got a pretty big game on Saturday to focus on," said the formidable fly-half. "We didn't turn up in Cardiff two weeks before but we showed big courage to react the way we did.

"We showed we can play pretty well and it would be nice to keep that momentum going until the end of the season. We've beaten two of the (Heineken Cup) favourites in Biarritz and Ospreys and our forward pack really made all the difference on Sunday. If we can keep playing like that who knows what will happen?"

If they do somehow manage to repeat those lofty standards then Gloucester will be in for a torrid time. Dean Ryan has vowed to stick with his side's adventurous style of play despite many critics insisting a more conservative approach might have helped topple Munster in their Heineken Cup quarter final.

As it turned out, Declan Kidney's men took a 16-3 win back across the Irish Sea with them to inflict Gloucester's sixth defeat in eight games.

"Gloucester will have been disappointed with the way they played and will be up for the game against us," added Jackson. "We were unhappy with the way we played towards the end of last season and the defeat to Gloucester in the play-offs was not one to remember.

"But we can't dwell on last year - we're a new team in another season and have to keep it alive. But If we lose on Saturday we're pretty much out of the Premiership running."

Jackson, the England-qualified New Zealand Maori, had sympathy for Gloucester's wayward wing Chris Paterson after the record-breaking Scotland international missed three easy penalties in the opening quarter of their defeat to Munster.

"Chris is a world class kicker as he showed in the World Cup and Six Nations," commented the influential half back. "He'll be more disappointed than anyone but it's just one of those days you have."

Alan Gaffney's troops are sixth in the table, six points behind fourth placed Leicester and only stand a realistic chance of sneaking into that final play-off spot by winning their remaining four games - tomorrow's clash plus homes games with Wasps and Bristol and a trip to Bath - along with some try bonus points. If they fail, they will be left with one route - the toughest of all - to achieve European qualification.

"We don't want to fall away after such a good start to the season," said Jackson, who again tops the Premiership's points scoring chart with 168. "Otherwise I suppose there would be no better way than qualifying for Europe by actually winning it (Heineken Cup).

"We're under no illusions as to how tough Munster will be. They've won it before and know what it's all about. We'll go into the game as massive underdogs but you never know what can happen on the day."

Fez Heads will head to Coventry in their thousands and Jackson, unusually outspoken about Sarries' fluctuating home gates prior to a packed Vicarage Road last weekend, believes they can make all the difference.

"Seeing a full house at Watford was a pretty special occasion and people that came for the first time might come back again," said the Kiwi. "There were quite a few Ospreys fans in the crowd but it was nice to keep them quiet. It was such an amazing picture from every angle."