A few papers reporting negotiations on extended contracts with three players (Jagielka and Howard are the other two) mention the fact that the discussions with Yobo might prove thorny:
Guardian
Guardian
Yobo has only 12 months remaining on his contract at Everton and could prove the most problematic of the three players regarding a new deal. The Nigeria international is understood to want parity with the club's highest earners in order to commit his future to Everton but he is unlikely to be offered a salary that matches, for example, Mikel Arteta's.