I'd rate Ralf Schumacher as a number 2. Dreadful driver who got in to F1 on the back of his brothers reputation. He was lucky to be more successful than Wilson Fittipaldi but to this day I have no idea how. When Schumacher junior and Montoya were together at Williams I very nearly stopped liking the team.
I seem to remember Ralf had the inability to overtake anyone.
I'm not quite sure how Tost can rate Verstappen and Sainz over someone like Buemi who he worked with for years and has been instrumental in Red Bull's development process both whilst he was at Torro Rosso and afterwards. I guess Buemi's name isn't as media friendly.
Liuzzi has multiple kart titles and holds the record for most wins in the old F3000 in a season - 7 wins to the point both Williams and Ferrari was interested
What was ridiculous was Red Bull dithered with his F1 career... firstly when in his 1st season Red Bull had either him or Klein and they decided to give them both equal contracts but then car share the 2nd car so he did not get time to settle