They topped Pool 4 prior to last week's action but were beaten 32-11 by Clermont at the Stade Marcel Michelin on Saturday afternoon, a result that sees them slip to third in the standings, four points shy of Clermont ahead of the return fixture.
And Easterby admits that there is no room for manouevre as they look to get back on track at the Parcy-Scarlets.
"We have to win, it's as simple as that. We showed we can compete with this team but we have to manage our game better and take our opportunities," said Easterby, who remains confident his side can progress despite the size of the task on Saturday.
"There is still everything to play for in this group and we have two home games out of three. This team can take confidence and positives from this encounter and, despite some battered bodies, we haven't picked up too many injuries, which is good.
"Hopefully we'll get some good numbers to support us at home next weekend after four games on the road. It will be a real boost to the players to come back and defend our proud West Wales home."
The Scarlets were well in the mix for large periods in France as they trailed by just three points at the break and threatened to cause a major upset.
But their hopes of becoming the first side in 67 games in all competitions and 16 in the Heineken Cup to defeat Clermont at the Marcel Michelin were ended by three tries in the third quarter as Clermont showed the power and pace that came so close to securing a first Heineken Cup crown last season.
"That last try was a bit of a killer blow given they had to go through 40-plus phases to get it but the boys could not have given more and we have to praise them for that.
"You have to hand it to our players, they gave their all. It's tough to lose in Europe but the boys put everything into that performance and I am very proud of the way they went about their business," added Easterby.
"On one hand we're bitterly disappointed we didn't get more out of the game, particularly as we held them to such a narrow lead of 6-3 at half time; on the other we can feel very proud of the way the players put in a performance with real spirit, effort and determination.
"We were down on possession and territory but we really scrambled well without the ball. We didn't spend enough time with the ball in the first half and the amount of work we put in to hold them probably told in the final stretch of the game.
"We did well to keep the pressure on them and stop their game in its tracks but Clermont just have that ability, with the depth and quality they have in their squad, to take it up a gear.
"It's pretty frustrating for us that they got a bonus point win with the fourth try in the last seconds I'm not sure that's justice for the amount we put in, given the way we held them throughout."