Guerra missed a move to Atletico Madrid last summer, but is back on their radar this summer.
New Atletico chief Carlos Bucera is eager to revive their pursuit for the young midfielder, but won't get a clear run.
El Chiringuito says Milan are also interested in Guerra.
For their part, Valencia are reluctant to lose Guerra, but will sell for the right price. The midfielder, meanwhile, is happy and settled at Mestalla, where he feels valued.