Cristiano Ronaldo made it six goals in as many Serie A games on Saturday as Juventus beat SPAL 2-0 to move nine points clear at the top of the table.

The five-time Ballon d'Or winner beat SPAL goalkeeper Alfred Gomis from six yards in the 28th minute at the Allianz Stadium – his ninth league strike for the Bianconeri.

Douglas Costa – one of six changes for Juve – impressed throughout for the league leaders, creating numerous openings that the hosts, including Ronaldo, were unable to convert.

Mario Mandzukic finally doubled Juve's advantage on the hour, the Croatia international sealing all three points with a simple tap-in after Costa's shot had stung the palms of Gomis.

Juve thought they had the game's opening goal after 11 minutes when a shambolic SPAL goal kick resulted in Felipe bundling a Costa cross into his own goal, but the visitors were spared as Gomis' initial kick had not exited the area before being played.

The impressive Costa went close with two efforts of his own in quick succession soon after, but his radar was slightly off from distance.

Ronaldo was much more clinical from six yards just before the half hour, though, the Portugal international timing his run perfectly to beat the offside trap and tap home Miralem Pjanic's free-kick.

Juve and Ronaldo should have doubled their tally early in the second half but somehow he failed to convert from a yard out, the ball dropping to him after Costa's shot had thudded against the post.

Costa's next involvement brought the second goal, his shot too hot for Gomis to hold and Mandzukic made no mistake from close range.

Ronaldo's quest for a second goal brought a fine late save from Gomis before an acrobatic bicycle kick sailed over, but it mattered little as Juve eased to ninth home league match without defeat.