The Hammers are not having the best of seasons so far, but did get a win over Manchester United last weekend.
Asked about the mood going into the Forest game, Lopetegui told reporters:
“A victory like last weekend (against Manchester United) is always important for our energy, but at the same time we know you can’t spend long thinking about the past. Things are very quick in football, and already it has been a short week and we are focused on Nottingham Forest.
“Always we are happy to win, but only for 24 hours or so before you’re thinking about the next thing, and the next challenge.”
On Forest, he added: “It’s going to be a very tough game. They are playing very well at the moment, and competing very well. They have good, technical players, and a very good coach, with clear ideas, and that’s why they’re doing so well in the league.
“They’ve beaten the likes of Liverpool, so we know this is going to be a demanding match, and we have to be ready. We’re expecting it to be a very big challenge for us, but I think the Premier League is the best competition in the world, so it’s like that every week!”
On their first game away from London this season, he added: “It’s the first time we’re playing out of London in the league this year. There are a lot of teams in London, but we are ready to go to Nottingham, to a different city, and we’ll be ready for the opponent, which is the most important thing.
“We know it’s going to be a big occasion, with a big atmosphere and high demands. We have to be ready to answer that.”