Not long ago, Tottenham and United were the tournament favourites, but apparently their "successes" in the Premier League forced the bookmakers to make their odds more reasonable. I don't know if Sociedad and AZ can knock them out, but I believe in Sociedad more. United had a grueling game with Arsenal, so maybe they won't have time to refocus on the Europa League. Besides, the overall result against Arsenal is positive, so it is difficult to expect United to show two positive results in a row 
Keep focusing on the bookmakers, they're not always right for real. Az will have to sit back, contain Tottenham Hotspur and hit them with counter attacks otherwise they'll be gone on Thursday night if they decide to come all out against Tottenham Hotspur away from home. Anything can happen, they have a chance to qualify if they can just defend the goals they'll score. I'm positive Manchester United will wrap things up against Real Sociedad, they won't struggle to get the win.. bias aside, they have what it takes to win this. Winning the Europa League Competition is the best shot they have so they could qualify for the Champions league. They are going all in for this shiiit.
Bookmakers are currently quoting this game as follows:
1.86 - 3.35 - 4.80
United are favourites, but they are a small favourite, with their chances of winning in regular time just over 50%. It makes sense that 14th place in the Premier League is still stronger than 11th place in La Liga, but we have seen United fail in even more obvious games on more than one occasion this season.
By the way, I thought more about the numbers and 1.86 looks unusually generous... apparently the bookmakers, as always, know more than us
Let me shock you Manchester United may not win the match if care isnt taking. And the bookmakers are also speculative when it comes to odd decision making. I wont agree that they know more than us.
One thing people don't know is that, is not odd that is playing the game rather it is humans that are playing, so what will determine if the bookmaker is right or wrong is if the game played according to how the odds where been given. By default Manchester united is the favorite and considering history too and lastly they are playing from home. Honestly speaking with you what Manchester united played Arsenal was unbelievable if not for the fact that Manchester united did not have a good finisher, they would have win Arsenal well and if they should play Real sociedad what they played Arsenal there's every tendency that Manchester united will qualify.