A national team plays a few crucial games a year, every game needs to be prepared into the smallest details, and only tactically good coaches can do that. Just look at how Iran was prepared to play Syria, and what that resulted in.
Iran has had a small advantage over teams like UAE, Syria and Kuwait for a long time now. But things have changed and the current Iran team is weaker than it used to be. At the same time, UAE and Syria have possibly got their best teams ever.
In the old days, Iran probably didn't even need a coach to beat teams like UAE and Kuwait. For many years Iran could field a B team and use coaches who were far behind good coaches in every aspect and still win crucial games in Asia. Those days are over as many countries are investing a lot in their football and closing the gap to Iran.
Whether we like it or not, Daei has been selected as the new head coach of Iran. Most football experts acknowledge that Daei is probably not ready yet to coach Iran, specially as he had a lot of issues with fellow national team players when he was still playing. Many of these players are still part of Team Melli. Ali Karimi and Eman Mobali are two important players for the upcoming Kuwait game and if either of them miss that game because of their previous problems with Daei, many would question Daei's appointment. If this happens, many would question whether a Team Melli with Daei but without Karimi or Mobali is stronger than one with Ghotbi and Karimi and Mobali?
At this point in time, Ali Daei needs to put his previous issues with other Team Melli players behind him, and pick the best players for the sake of Iran, and national pride, rather than based on what might have happened in the dressing room between him and others. Daei is now serving his country as the head coach as he always wished, so now is the time to be a hero again, now is the time to be the old Ali Daei! The same goes for the players like Karimi. They need to put the past behind them, and look at the bigger picture here, as qualification to World Cup is at stake.
Karimi has already taken a professional stance on this whole issue, and has publicly backed Daei. One hopes for more of the same.