Sir Alex has again been impressed with the standard in this season's Champions League and says every side left in the competiton could pose a threat.
"The standard has been very high this season – you can see that by how tight some of the groups have been. So it’s difficult to say who you’d want [in the last 16]," he told ManUtd.com.
"A few people maybe thought Stuttgart would be the weakest team, but they’ve got a new coach now [former Tottenham boss Christian Gross] and things change with new coaches.
"We’re pleased to have the second leg at Old Trafford and hopefully we can use that to our advantage."
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