"I think it adds more to the motivation rather than pressure", Djokovic said of being the first to win all nine Masters.
"I wasn't feeling great for a set and a half, I had some stomach issues", Djokovic said in his on-court interview afterwards. "Obviously I didn't have a lot of practices to try to recover, so I had to manage a little bit".
'But, you know, I need to definitely play better than I have in the first couple matches.
There was one notable upset in the men's bracket before the rain arrived.
The world No. 10, who missed the latter part of the 2017 season with an elbow injury that required surgery but captured his 13th Grand Slam title last month at Wimbledon, will next take on either fifth-seeded Bulgarian Grigor Dimitrov or Germany's Mischa Zverev. He won his first Masters title at the Western & Southern a year ago without dropping a set.
B.C. declares state of emergency over wildfires
Additional federal resources and personnel will arrive in the province in the coming days in response to the state of emergency. The statement points to fine particulate matter from the B.C. wildfires as the reason why a haze can be seen over the region.
Defending tournament champion Garbine Muguruza had a third-set meltdown and lost to Lesia Tsurenko 2-6, 6-4, 6-4 after a critical double fault.
After being given medication at the change of ends, Djokovic looked more like himself in the humidity as he took the second set and then won five consecutive games at the start of the decider. Nothing could separate them in the mid-range and longer points but Novak had the upper hand in the shortest rallies up to four strokes, finding his range after a poor opening set and celebrating a win despite taking a medical timeout and some pills.
Halep returned and ran off four straight games against the 58th-ranked Tomljanovic before a storm moved in.
And when Djokovic got back to business he lost only one game to claim the final two sets 6-2, 6-1.
Australian 16th seed Ash Barty beat Estonian Kaia Kanepi 7-5, 6-3, while Gstaad champion Alize Cornet was crushed 6-2, 6-0 by Ekaterina Makarova.
A trainer applied a bandage to the third-seeded Stephens' right thumb between the third and fourth games of the second set.