Decoy - 'lure or entice (a person) away from their intended course, typically into a trap'.
Guessand does bring energy to the team and puts in a shift. But his footballing skills need a lot of work.
Can only guess that Unai considers Guessand as playing a pivotal role in his strategy. All players have to be marked and Guessand does hug the line, cut inside, get in the box and also carry out his defensive duties. Perhaps Unai is treating him as a disruption to the opposition, a decoy. Who is going to mark him, the full back, midfielder, a center half? This can cause confusion and create spaces for others to exploit.
We have tonnes of quality and creativity throughout the team and maybe Unai puts more emphasis on Guessands 'nuisance' value than he does his current footballing skills.
Unai is a tactical wizard and the results speak for themselves.
Perhaps I am being to polite.