Carroll endured a frustrating spell on the sidelines in the first half of the campaign due a heel injury.
However, since returning in January, Carroll has put in a series of assured performances and was among the goalscorers as West Ham secured a vital three points in Monday's visit to Sunderland.
Carroll last featured for England a 5-0 victory over San Marino in a World Cup qualifier in October 2012, but Downing believes the former Liverpool man can be a contender for Roy Hodgson's 23-man squad in Brazil later this year - if he continues to score goals.
Speaking to West Ham's official website, he said: "It was a tremendous header (against Sunderland). We work on things like that to target Andy at set pieces.
"It was a great leap and a great header. It's a good goal for him and he wants to get as many goals as he can to get picked for the World Cup."
Maximum points at the Stadium of Light leaves West Ham 11 points clear of the relegation zone.
Downing is refusing to rest on his laurels, however, and is focused on the home encounter with former club Liverpool on Saturday, with the league leaders heading to Upton Park unbeaten in 13 top-flight outings.
He added: "I wouldn't say we're out of sight. For us the target is to finish as high as we can, we're not just sitting happily now because we've got 37 points.
"We want to get as many more points as we can before the end of the season. Liverpool is a big game at the weekend, we can do other teams a favour and ourselves a favour by getting into that top ten position."
