Murray has 4-0 love record, and has never dropped a set, against Querrey but with the exception of this years Wimbledom all of those go back at least 2 years and Querrey has made big improvements since then.
If Murray plays well his all round game should be far to good for Querrey but if he doesn't it could be a tricky match. Fate has seemed with Querrey this week. Both Schuettler and Tipsarevic had all but won their matches against him only to throw it away.