The Merseyside outfit are fighting for the Premier League title, while the Hammers are aiming for a top-10 finish before the end of the season.
"It's nice to play against your old teams and I'm sure Andy and Joe Cole are looking forward to it," Downing told the club's official website. "We're in for that top 10 spot and it's tight, so we want to do ourselves and the other teams a favour.
"[Liverpool's] forward line is frightening at the minute. The goals are coming from everywhere, but we'll make it hard for them at our place.
"When I was playing for Liverpool it was always hard against West Ham at Upton Park. It's going to be difficult, but a good win on Monday breeds confidence and we fancy ourselves against anyone at home."