Just three days after lifting the FA Cup, Wigan were consigned to the Championship following a 4-1 defeat by Arsenal at Emirates Stadium, ending their eight-year stay in the top-flight.
But Martinez says that the Latics are not an easy target for rival clubs despite having lost their Premier League status.
He said: "Whatever happens here, we have very talented players. You cannot stop a player from going to a different level. What you can affect is the value and timing.
"We are not in a position where we have to balance the books. We will never be in a position where we have to undersell our players.
"We sold Victor Moses and Charles N'Zogbia and invested in three players. As I have said, once Manchester United sold Cristiano Ronaldo, no club in the world has a chance of retaining their players."
Wigan play Aston Villa on Sunday at the DW Stadium in their final game of the season.
It could also be Martinez's last with the club having been linked with a number of other jobs.