Garner, 25 has found opportunities at Vicarage Road limited but has managed to rack up 14 (+8) appearances since his move from Nottingham Forest in August 2011 and scored his only goal in a 2-0 win at Millwall.
However the Hornets have recently been bought-out by rich Italians and with competition for places with Chris Iwelumo, Troy Deeney and Gavin Massey as well as any new signings this summer is likely to see Garner slip down the pecking order.
Blades boss Danny Wilson is in the search for a new striker after losing Ched Evans as well as releasing James Beattie following the end of his contract and is likely to make a £100,000 move for Garner who lists his former clubs as; Blackburn Rovers, Carlsile United, Nottingham Forest, Huddersfield Town (loan) and Scunthorpe United (loan).