If he didn't pick Elizabeth Warren for the Consumer Financial Protection Bureau, he's not going anywhere near Krugman for SECTREAS. The fact is that Obama and Krugman don't see anywhere near eye-to-eye, so that would take the Team of Rivals concept way too far.
SECTREAS has to be someone that can soothe things in the back room when POTUS gets out in front of a sticky subject to the banksters. Krugman wouldn't be let in the door, thus rendering him useless to Obama.
/jordan