Inter Milan's run of seven successive Serie A wins came to an abrupt end on Sunday as they fell to a 1-0 defeat by relegation strugglers Lecce, a loss made all the more bitter by AC Milan's 3-0 win over Cagliari which saw their rivals tuck in just a point behind leaders Juventus.
Uruguayan Guillermo Giaccomazzi struck for Lecce to give them their first home win of the season - they had previously taken just two points from the 27 available at home - while their 'keeper Massimiliano Benassi was in superlative form, denying Inter on several occasions.
Lecce's win took them to three points from safety, fourth from bottom Siena having lost 2-1 earlier on Sunday to Fiorentina.
Inter's loss leaves them nine points adrift of Juve, who beat Udinese 2-1 on Saturday, and AC Milan rubbed it in by sweeping aside Calgiari with goals from Serie A's leading marksman Zlatan Ibrahimovic, who bagged his 15th goal of the campaign with a fine freekick which sailed in past helpless keeper Michael Agazzi.
After the Sweden international's opening salvo on 32 minutes Antonio Nocerino swiftly made it 2-0 with his seventh of the season shortly before the break before Massimo Ambrosini swept home the clincher with the outside of his right boot on 75 minutes.
The win moved the defending champions onto 43 points from 20 games with Juve having moved to 44 after a brace from Alessandro Matri saw off fellow high-riders Udinese in Turin on Saturday.
Matri's efforts nudged Juve over the line after a fine strike from Antonio Floro Flores had threatened to bag a point for the visitors.
Udinese stay third, six points off the pace, with Lazio in fourth, a point clear of Inter, after the Rome-based outfit kept in touch with the battle for Champions League places with a 3-0 win over Chievo, two late goals from veteran German international striker Miroslav Klose sealing the victory.
Capital rivals AS Roma lost ground after being held 1-1 by Bologna despite a superb goal from a freekick by Bosnian international Miralem Pjanic.
Napoli went down to a surprise loss as, having ended Inter's defence of their Italian Cup trophy on Wednesday, they went down 3-2 at mid-table Genoa and now trail Juventus by 15 points.
Napoli had only last month walloped Genoa 6-1, but this time round they found themselves trailing 3-0 before rallying - but to no avail.
A double from Argentinian Rodrigo Palacio, taking him to 11 for the season, and a first goal in Genoa colours from veteran Italian World Cup winner Alberto Gilardino, who joined in the transfer window from Fiorentina, set Napoli an almost impossible task.
They made a game of it, but only in the last 10 minutes as Uruguayan Edinson Cavani and Argentinian Ezequiel Lavezzi struck in the 80th and 82nd minutes respectively.