Everton keen on West Ham midfielder Pedro Obiang, according to the Mirror, but would have to pay at least £15m for his services.
AC Milan and Sevilla are also said to be interested in the 25-year-old, although the Hammers would like to keep the Spaniard beyond his current deal.
But Koeman is in pole position to keep Obiang in the Premier League after two seasons in England, with the ex-Sampdoria star targeted to compete for a place with Gareth Barry alongside Gueye.
Obiang has two years left on his contract at the Olympic Stadium and West Ham are looking to extend his deal beyond 2019
But they will also stand to make a huge profit on the £4.3million they paid Sampdoria two years ago should they cash in.
His form this season made him runner-up in the Hammer Of The Year award which was won by Michail Antonio.