90%?
Doubt it.
Twenty-20 is a form of the game were absolute hack sloggers can have a career in.
Test cricket sorts out the men from the boys. Gayle, in this respect, is a boy.
He averages 36 or lower (and 45 is the new 40 when you take into account the general batsmen-friendly wickets prepared across the world) against Us, Australia, Sri Lanka, India & Pakistan. His only notable average is against South Africa, but I'm sure next series around (if he's still playing test cricket) he will be pwned by Steyn, Morkel and co.
I'm not surprised he isn't a fan of test cricket- he's a poor test batsman, whereas (along with other batsmen who can't play a cricket shot for love nor money such as Afridi, Yuvraj, Dhoni, McCullum etc) he can be a star in T-20.
Strauss however realizes that your quality is judged on how good a test match player you are.