By contrast, Djokovic, who breezed past Bosnia's Damir Džumhur in just 55 minutes on Tuesday, was made to work much harder for victory against Hungarian Márton Fucsovics, dropping the first set to the world number 36, and having a tough fight in the second, before running away with it 6-1 in the third.
The world number one survived a huge scare to eventually triumph 4-6, 6-4, 6-1 and admitted his opponent was "very close to the win".
Djokovic, who has won the last two Grand Slams - at Wimbledon and the US Open to take his majors total to 14 - completed the match in under an hour by predictably converting his first match point.
Djokovic added: "I knew his qualities and especially in the slower conditions, so I did expect that it was going to be a match with a lot of rallies and very physical and that has proven to be the case".More news: Trump Gives US Troops Four Months to Leave Syria Amid Criticism
Up next for Djokovic in men's singles is Nikoloz Basilashvili of Georgia.
Djokovic - the victor of this event in 2016 and 2017 - has now won 12 matches in a row in Qatar and will face Andrey Rublev or Nikoloz Basilashvili in the quarter-finals.
The two square off against David Goffin and Pierre-Hugues Herbert next.
If he wins his last eight match, Djokovic is on course to meet Stan Wawrinka in the semifinals after the Swiss also won on Wednesday, beating Chile's Nicolas Jarry 6-4, 7-6 (3).
Yet the top seed got back on level terms when Fucsovics stopped play to challenge a line call when facing set point on his own serve, only for HawkEye to show Djokovic had just clipped the baseline.