Cristiano Ronaldo is doubtful for Real Madrid's trip to Levante on Sunday after picking up an ankle injury against Dinamo Zagreb in mid-week.The Portugal international was on the receiving end of some strong tackles in his side's 1-0 Champions League victory.Ronaldo's ankle needed to be stitched after the final whistle.The attacking midfielder will now have to pass a late fitness test before being named in Real Madrid's squad.The 26-year-old has started the 2011-12 La Liga campaign strongly, netting four goals in two games so far.Los Blancos lead the early La Liga table on goal difference from Valencia and Real Betis.All three boast a 100 per cent record from their opening two fixtures while defending champions Barcelona have four points from a possible six.