Hernandez has passed a medical and is joining the Whites on a temporary basis from Qatari club Al-Arabi.
Al-Arabi signed Hernandez from Swansea City - a club where he played alongside Leeds’ head coach Garry Monk in 2014 - but he spent most of last season in La Liga on loan at Rayo Vallecano.
Leeds are also continuing to pursue Sunderland midfielder Liam Bridcutt but are yet to make decisive progress with that transfer and the club remain in the market for a centre-back and a full-back.
Hull City attacking midfielder Mohamed Diame is being lined up by Newcastle United as a possible replacement for Moussa Sissoko.
The Magpies are yet to sell the French international - who is widely expected to leave Tyneside this summer - but want Diame to boost their midfield.
The Senegal international is said to be interested in a move to St James’ Park - with reports suggesting that the north-easterners have bid for the 29-year-old.
Diame has just one year left on his Tigers’ deal.
Middlesbrough have been linked with a move for Manchester United defender Paddy McNair, as they seek to boost their defensive numbers.
Meanwhile, Boro duo Adam Forshaw and David Nugent are on the radar of Championship outfit Wolves, while coach Aitor Karanka has confirmed that either Tomas Mejias or Dimi Konstantopoulos will move to pastures new, with the Teessiders having brought in two senior goalkeepers this summer in Victor Valdes and Brad Guzan.
Birmingham City are mulling over whether to make a third approach for Sheffield United forward Che Adams, who has held talks regarding his future with Blades chief Chris Wilder.
The Blades rejected an improved bid from the Blues late last week for Adams, with their latest offer - a package potentially worth around £1.7m - rebuffed.
Wilder will reach a decision regarding trialist Chelsea defender Alex Davey shortly.
Bradford City manager Stuart McCall is targeting three more signings to boost his ranks - with a centre-half, central midfielder and a striker on his wish-list.
Youngsters Daniel Devine and Reece Webb-Foster could feature in a behind-closed-doors game with Barnsley today and McCall will today make a call on whether to hand trialist Rory McKeown a deal.