West Ham have had a £7m bid turned down by Hull City for Scotland left-back Andrew Robertson, according to Sky sources.
The Hammers have been forced into the left-back market after Aaron Cresswell was injured for up to four months with knee ligament damage on Monday.
Creswell missed just one Premier League game over the past two seasons but was left writhing in agony in the closing stages of Saturday's pre-season win over German side Karlsruher in Austria.
Robertson, 22, was instrumental in Hull's promotion campaign to the Premier League last term, making 52 appearances in all competitions and scoring four goals.
He signed for Hull from Dundee United for £2.8m in 2014 and has gone on to play 77 times for the Tigers. Glasgow-born Robertson also has 10 caps for Scotland.
West Ham have been plagued with injury problems already in pre-season, with Manuel Lanzini suffering a knee injury with Argentina ahead of the Olympic Games in Rio.
Summer signing Gokhan Tore also needs a scan on his own knee problem after being hurt in training on Monday.