^^Anyone who worked with Ahmed Shah Massoud would do as Afghan leader!
BTW your link says that Atta Muhammad Nur is an ethnic Tajik. Don't you see any chances of Abdullah Abdullah trying his luck for the second time?
The consensus within the opposition is that there needs to be one single unified candidate in order to avoid splitting the vote. So far Nur appears to be that guy. He is like our Narendra Modi, in a sense. He already has administrative experience and has done a lot for Balkh province including education, afghanistan's only railway, factories, real estate, etc. In short, he has the track record. I will talk about Abdullah down the page.
Where is Abdullah Abdullah?
In the 2009 elections, Abdullah was thoroughly outmaneuvered by Karzai, though Karzai did cheat and stuff the ballot box.
In Afghan elections, Tajiks and Pashtuns tend to vote along ethnic lines, thus none can win an election outright. Thus, they have to get the vote of the Hazara and Uzbeks, who tend to vote for whomever makes them the tallest promises. Karzai capitalized on this quickly and thus he won all but the most Tajik-heavy provinces. The only reason the vote went to a second round was because people in the Pashtun areas didn't vote in high enough numbers due to insecurity (though this was supplanted by karzai cronies stuffing the ballot box.) Karzai is doing the same this time around by making the vote in March, which would prevent people in the north, where there will still be snow in some areas, from voting in big numbers
But Abdullah really looked weak to everyone when he refused to run in the run-off. handing the election over to Karzai. Nowadays he is mostly a spokesman and senior strategist for the opposition, a role which i think suits him best.