Manchester United will intensify their pursuit of Juventus midfielder Arturo Vidal after they completed the signing of Ander Herrera.
Southampton left-back Luke Shaw should also complete his protracted move to United as Louis van Gaal's overhaul of a beleaguered squad gathers momentum.
Chilean Vidal only signed a contract extension with Juve until 2017 in December last year, however that was as much an admission of the Italian champions' willingness to sell him for a greater fee.
Juventus announced a €6.5m dip in profits for the first half of the 2013-14 financial year and the club's debt has increased to €188m from €160m. The Bianconeri are believed to be receptive to the idea of selling one of their outstanding performers and United have confirmed their interest.
Vidal was scouted by former United manager David Moyes in January and new United coach Van Gaal is also an admirer. Vidal played against Van Gaal's Bayern Munich for Bayer Leverkusen before he joined Juve in 2011.
A tireless box-to-box midfielder, since Juventus bought Vidal they have won three successive Scudetti and the 27-year-old scored 18 goals last season, having hit 13 the previous campaign.
Vidal is currently preparing for Chile's round-of-16 World Cup knockout tie with Brazil on Saturday, having started in their wins against Australia and Spain. He has been struggling with inflammation in his right knee following an operation on his meniscus last month but is expected to start against the hosts.
Van Gaal's focus on United's midfield will please supporters vexed by the club's problem position. Marouane Fellaini became the first central midfield signing United made since 2007 last year while the underwhelming quartet of Tom Cleverley, Darren Fletcher, Michael Carrick and Anderson are all out of contract in 2015.
Bayern Munich's Bastian Schweinsteiger and Roma's uncompromising Dutchman Kevin Strootman are also in Van Gaal's thoughts, although the latter is out with a knee injury until October.
Herrera completed his Old Trafford move 10 months after United failed with a summer deadline day offer last year and is the first arrival of the Van Gaal era.
The 24-year-old Basque midfielder has signed a four-year contract, with an option to extend it for a further year.
— Manchester United (@ManUtd) June 26, 2014
"Signing for Manchester United is a dream come true," Herrera said. "I have played at Old Trafford for Athletic in the Europa League and it was one of the highlights of my career so far.
"I have joined United to do all I can to help the team reach the club's objectives. Having arrived on Tuesday, I’m excited to now be living in Manchester and I can’t wait for my first game in United’s famous red shirt. I will never forget my time with Athletic Club and I’d like to thank the fans and staff for all their support and, above all, wish all my fantastic former team-mates all the best for the future."