Downing had a mixed spell last term, playing incredibly well as a number 10 for the first half of the season, before struggling to replicate that form in the second half of the campaign. He was moved back out to the wing by Sam Allardyce, and became predictable once again by always pushing the ball onto his stronger foot.
Considering his struggles towards the end of the season, and the signing of Payet, it could be suggested that Downing should be sold. However, the Hammers should keep ahold of the English winger, seeing as he will fulfil a useful role during the 2015/16 season.
West Ham have real ambitions to progress well in the domestic cups, the Europa League and the Premier League, and having strength in depth will be vital. Downing is certainly good enough to play for a number of top half Premier League sides, and although he may now be pushed out of being a regular first-team player, he will play a key role as a rotation option.
The Hammers need a squad capable of competing on a number of fronts, and Downing has proven he can play that role. They should not be selling him to a Premier League rival, and should be looking to keep him involved in the first-team set-up for his ability, experience, and, most invaluably, his knowledge of European competitions.