The Scarlets lost 49-16 in Clermont Auvergne a week ago, with winger Morgan Stoddart sent off for two yellow cards.
But while a win would all but end the Scarlets' hopes of reaching the quarter-finals, Easterby is optimistic that a win would put his side right back in contention.
He said: "One thing we can't afford to do on the weekend is lose the game and leave ourselves with no wins from two.
"We're not down at all about what happened in Clermont.
"What's great about this competition is that we're playing the European champions the week after Clermont.
"It's heightened everyone's awareness and positivity going into this game.
"If we win, I could see Exeter causing a bit of a surprise down in Sandy Park - I don't think Clermont will be looking forward to going there.
"Then it could all be a level playing field after round two."
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