The winger is preparing for his third loan spell in the Championship after struggling to make an impact at Sunderland.
The Swiss international signed on loan for Nottingham Forest this week.
Bournemouth sold the winger to Newcastle United earlier this summer.
Newcastle United lost 1-0 to Fulham at Craven Cottage.
The Frenchman is set to join the Hammers this weekend.
The 24-year-old has left the Scottish Premiership side for Rotherham United.
Newcastle United were beaten by Fulham in their Championship opener on Friday.
Don Goodman doesn't think Leeds will be challenging the top eight this season.
The Gunners have been in impressive form in pre-season so far.
Many are hoping to see Rangers challenge Celtic for the title next season.
Leeds United were interested in signing Marcus Maddison from Peterborough United last January.
Should Leeds United sign players in the January transfer window?
Tottenham Hotspur won against West Bromwich Albion in the Premier League on Saturday.
Leeds United won against Derby County in the Championship on Friday.
Villa sold Gestede to Middlesbrough for £6 million earlier this month.
Tottenham Hotspur boss Mauricio Pochettino has suggested that Vincent Janssen wasn't ready for regular starts in the Premier League.
Tottenham Hotspur have moved to second in the Premier League table.
The Spaniard was in superb form against Derby County yesterday.
Leeds United won against Derby County in the Championship on Friday evening.
Leeds United are keen to re-appoint Ian Broomfield.