I feel kinda conflicted reading that article. I considered Tannehill to be a pretty average QB at best and wouldn't trade for him, it's also hard to take QB evaluation seriously from any former Cleveland Browns GM. I know Lombardi is a "consultant" to the Pats, but it's kinda one of those opposites thing. When the Pats are evaluating a player they ask if he would draft or trade for the player and do the opposite of what Lombardi advises.
I don't know about a 3rd, but for a team like the Cards, a 4th or 5th might make sense to have Tannehill as a solid backup QB.