The Italy international midfielder drove home with a little more than five minutes remaining to secure three points and ensure that the Bianconeri remain top of the Serie A table.
The Bianconeri took the lead 14 minutes in courtesy of a free kick from Andrea Pirlo, who struck the bar with another sublime set piece later in the half. However, the two sides went in level at the interval, with Emanuel Calaio heading home just before the halftime whistle.
Juventus bossed the second period, but it seemed that its efforts would prove in vain; however, with about five minutes remaining, Marchisio came to their rescue to steal a win that keeps the defending Serie A champion on top of the table.
Juve had gone into the game on the back of a fortuitous draw at home to UEFA Champions League foe Shakhtar Donetsk, and the defensive frailty that was on show in Turin on Tuesday night was in evidence again at the Artemio Franchi.
Siena should have been ahead inside two minutes, but Alessandro Rosina, who was a constant thorn in Juve’s side during the first half, miscued his first-time strike, and the ball ended up bouncing harmlessly into the arms of Gianluigi Buffon.
While the visitors looked vulnerable at the back, Sebastian Giovinco and Mirko Vucinic were causing problems every time they picked up possession at the other end of the field, and it was no surprise that the pair played a key role in the Bianconeri’s opener.
Vucinic left two Siena defenders trailing in his wake with a wonderful turn in midfield before slipping the ball wide to Giovinco, who ended up on the deck after bamboozling Felipe with his quick feet. Pirlo took the subsequent free kick and found the bottom corner by firing the ball underneath the feet of the players in the defensive wall, who had collectively jumped in an attempt to make the playmaker’s task more difficult.
The goal unsurprisingly settled Juve and they could count themselves unfortunate not to have doubled their lead before the break, with Pirlo crashing another set-piece against the cross bar on 40 minutes before Claudio Marchisio drew a flying save out of Gianluca Pegolo moments later.
Siena continued to threaten, and veteran striker Calaio, right on half-time, powered home a header at the far post after Angelo had beaten Paolo De Ceglie to the byline before whipping over the most inviting of crosses.
Juve struck late, though, and deservedly so, and Giovinco was key, as the former Parma man blew past a couple of players before crossing into the area. The ball was nodded back across the box by Giorgio Chiellini, and Marchisio arrived right on cue to drive the ball through a crowd of players and past Pegolo, securing Juve's sixth win from seven outings this season.