Hernandez joined the stellar line-up of attacking talent at Real Madrid on a season-long loan from Manchester United.
The reigning European champions have the option to buy the 26-year-old Mexico international at the end of the season, with his on-going Old Trafford deal running until June 2016.
Negredo returns to La Liga after just a season away, joining Valencia on loan with a commitment to completing a permanent move next year having collected Premier League and League Cup-winners medals with Manchester City.
The Spain striker adapted seamlessly to English football, scoring 23 times in all competitions for City by late January.
But a shoulder injury hampered his progress and Negredo finished the season with a 16-game goal drought, missing out on a place in Spain's FIFA World Cup squad.
The 29-year-old is currently nursing a broken metatarsal sustained during pre-season and was tipped to miss out on a place in City's UEFA Champions League squad - restricted to 16 non-homegrown players as part of the club's punishment for breaching Financial Fair Play regulations, while reports also claimed Negredo failed to fully settle in England.
Valencia also moved to acquire Filipe Augusto on a season-long loan from Portuguese team Rio Ave, with the 21-year-old midfielder plotting the same path as coach Nuno Espirito Santo to the Mestalla.
There were deadline day outgoings from the club, with attacking midfielder Jonathan Viera joining Belgian side Standard Liege.
Forward duo Helder Postiga and Jonas were released from their Valencia contracts, with the former joining Deportivo along with wideman Juanfran and defender Sidnei - on season-long loans at the Riazor from Real Betis and Benfica respectively.
Italy winger Alessio Cerci finalised his move from Torino to Atletico Madrid on a three-year deal.
The former Fiorentina and Roma player became the eighth player to join the Spanish champions during the transfer window, for a reported €16million (£12.6m) fee, and joins Mario Mandzukic, Raul Jimenez and Antoine Griezmann in a remodelled forward line.
Three defenders left the Vicente Calderon, with Toby Alderweireld joining Southampton on-loan for the season, Silvio Pereira opting for another campaign at Porto and Emiliano Insua one of three arrivals at Rayo Vallecano.
Ghanaian midfielder Mohammed Fatau moves to Rayo on a season-long loan from Granada with an option to make the deal permanent included the 21-year-old's terms.
Former Liverpool full-back Emiliano Insua also arrived on a year-long loan at the Campo de Futbol de Vallecas, while experienced goalkeeper Tono Martinez secured a two-year contract on a free transfer following his release by Elche last month.
Jose Canas was another Spanish player returning home the Premier League as he joined Espanyol from Swansea on a free-transfer.
The 27-year-old signed a three-year deal with the Barcelona club having joined Swansea from Real Betis last June and making 23 appearances.
Granada looked to sustain their assured start to the season with a double swoop to bring in Portugal Under-21 left-back Luis Martins and fellow 22-year-old Eddy Silvestre.
Former Benfica youth product Luis Martins leaves Gil Vicente for an undisclosed fee until 2018, while Silvestre arrives on loan with a view to leaving financially troubled Segunda B outfit Real Murcia on a permanent basis.
La Liga newboys Cordoba also added two to their number, with former youth-team product Fede Vico returning on a year-long loan from Anderlecht and Algeria striker Nabil Ghilas securing similar terms from Porto.
Elsewhere, Eibar brought in Serbian forward Dejan Lekic on a one-year contract after he was released by Turkish club Genclerbirligi and Udinese's 26-year-old Brazilian defender Naldo settled on a season loan with Getafe.