John Mayer has a message to Dallas football fans: Back off!

The singer took to his blog Tuesday to defend his ex, Jessica Simpson, who some have been blaming for the poor performance of her NFL-star boyfriend Tony Romo.

The Dallas quarterback struggled toward the end of the season as Simpson watched from the stands, causing talk of a possible “Jessica Jinx.” More recently, he was widely criticized for vacationing with Simpson in Mexico before Sunday’s playoff loss to the ...