Arsenal have reportedly identified three targets as potential replacements for midfielder Aaron Ramsey next summer.
Ramsey looks certain to leave the Emirates Stadium when his current deal expires at the end of the season, having seen the offer of an extension withdrawn by the club.
The Gunners are understood to have made a final decision to allow Ramsey to leave the club, even on a free transfer, and are now working on possible alternatives to the long-serving Welshman.
Cagliari's Barella has previously been linked with Liverpool and Chelsea and is thought to be keen on a move to the Premier League, although Roma and AC Milan have also been credited with an interest.
Paraguay international Almiron has scored 12 goals and provided 13 assists for MLS side Atlanta United this season and is likely to be available for a cut-price fee, although Arsenal could face competition for his signature from London rivals Tottenham Hotspur and West Ham United.
Herrera, meanwhile, currently plays for Porto and will be a free agent this summer having already rejected three contract offers.
Ramsey himself is a man in demand too, with a host of clubs including the likes of Manchester United and Liverpool interested in the 27-year-old.