Real Madrid fans will certainly criticize Xabi Alonso if the expected improvement never happens, and I think he knows what's at stake. The victory over Osasuna was a great start, and it's highly likely that Real Madrid will also win their next match against Real Oviedo. Overall, Xabi Alonso seems capable of meeting expectations.
It's undeniable that Xabi has received some criticism for building the Real Madrid squad. He started with very high expectations, but so far, Xabi has been deemed incapable of doing so. It's a process, but we'll have to see how long it takes to adapt to his tactics. A big club like Real Madrid should be able to do it much faster and much better.
But if we look at the results of several signings under Xabi so far, both in the first leg and in La Lig, the progress of his squad has not been that impressive, and in fact it seems less organized, especially the midfield and forward lines which are known to have a very high skillful squad, but really bad attacking styles and effectiveness.