The Serbian motored through the first set, but Seppi then upped his game and made Djokovic work very hard to see out the match in three.
The Australian Open confirmed Djokovic's path through to the last 16:
Djokovic delivers... The defending champ makes the R16 for 10th straight year, downing Seppi 6-1 7-5 7-6(6). https://t.co/ZWYzVtB95a2016-1-22 10:39:41
Djokovic made a flying start on Margaret Court Arena, moving into a 3-0 lead inside 10 minutes. He broke again for 4-0 and, although Seppi got a game on the board in his third service game, the top seed sealed the opening set in just 25 minutes.
It looked as though it might be an easy day for Djokovic, but Seppi stepped up his game in the second set.
The world No. 29 was much more aggressive with his groundstrokes, going for the lines and hitting them more often than not.
As tennis analyst Brad Gilbert noted, it was an impressive increase in intensity from Seppi:
Brad Gilbert @bgtennisnation
Wow Seppi has turned things around a bit in 2nd set up 3-2 vs Djoker2016-1-22 09:11:44
Though Djokovic gave little away on his own serve, Seppi responded in kind, and the set looked to be heading for a tiebreak at 5-5.
However, at the final opportunity, Djokovic claimed the key break. A stunning 32-shot rally on break point saw Seppi on the brink before regaining his composure with some terrific saves, but Djokovic's persistence eventually did the trick.
He served out the second set as the match ticked toward the 90-minute mark to leave Seppi with a mountain to climb.
The 31-year-old's head did not drop, though, and he continued to cause Djokovic trouble. The five-time champion's unforced error count was surprisingly high—he registered 14 and 19 in the second and third sets, respectively, compared to just four in the opener, per the Australian Open.
Seppi still struggled to trouble his opponent's serve, but he kept the pressure on Djokovic with some inch-perfect backhand winners down the line.
Again a tiebreak looked inevitable at 5-5, and this time Seppi held firm, per tennis writer Chris Goldsmith:
Chris Goldsmith @TheTennisTalker
Seppi does well.... holds for 6-5 and worst he can do it a 3rd set tie-break against Djokovic #ausopen.. Novak leads 6-1 7-5 5-62016-1-22 10:23:22
The first three points of the breaker went with serve, but Seppi's missed backhand gave Djokovic the first mini break, only for the Italian to regain parity after a stunning forehand return for 4-3.
A backhand error on serve from Djokovic handed Seppi two set points, but he proved his No. 1 status as he battled back to 6-6.
Djokovic then forced an error from Seppi to earn his first match point, and he made no mistake, as his ever-consistent first serve proved too good, and he claimed victory after 141 minutes.
Djokovic will now face Gilles Simon in the fourth round, with the French 14th seed having downed Federico Delbonis to make the last 16.