Barcelona manager Ronald Koeman has admitted that he feels nervous about the future of Lionel Messi, who is no longer linked with the club after his contract expired.Messi, who became a free agent on July 1, has agreed on most terms in a new contract but has had to wait by Barcelona, who need to lower their salary budget by a huge 170 million pounds to get back under the salary cap before they can sign Messi.The scope of the information means that there is a real possibility that Barcelona will not be able to write about…