Managing his workload by playing only Doha and Indian Wells since - reaching the final of both tournaments - has paid off.
Entering this contest, it felt like Draper would be a different proposition for Alcaraz.
Draper had not dropped a set in a tough run to the last four, having beaten prodigiously talented teenager Joao Fonseca, former top 20-player Jenson Brooksby, world number four Taylor Fritz and Australian Open semi-finalist Ben Shelton.
The key had been consistent serving, incisive returning and sharper movement - all underpinned by having greater confidence in his body.
Image source, Getty Images
Image caption,
Draper ended Alcaraz's 16-match winning streak at the BNP Paribas Open in Indian Wells
Winning eight of the opening nine points helped Draper move 3-0 ahead, securing a double break at 5-1 with the help of wild forehand errors from the Spaniard.
Bemusement among the pro-Alcaraz crowd was evident. Draper remained focused despite the discord and confidently served out the opening set with just 23 minutes gone.
Alcaraz, audibly agitated, had won just 10 points. Afterwards the reigning French Open and Wimbledon champion said it was "probably one of the worst" sets of his career.
Surely he could not continue to play that badly? After saving a break point in the opening game of the second set, Alcaraz's level improved considerably.
Dominating from the baseline with more fluid groundstrokes, and finding outrageous angles at the net, Alcaraz drained Draper to quickly take the match into a decider.
Draper had lost energy and Alcaraz now appeared to be the favourite.
But, in another sign of his growing self-assurance, Draper reset after giving himself a pep-talk in the bathroom - and it was Alcaraz who wilted.
"I looked at myself in the mirror and was like 'you need to really get your stuff together'," said Draper.
"I had to knuckle down and that was it."
Image source, Getty Images
Image caption,
Olivia Nicholls is the British number one in women's doubles
Meanwhile, Britain's Olivia Nicholls missed out on a first WTA 1,000 title after losing in the women's doubles final.
Nicholls, 30, and her Slovakian partner Tereza Mihalikova were beaten 6-2 7-6 (7-4) by Dutch player Demi Schuurs and Asia Muhammad of the United States.
Nevertheless, it has been another productive week for the pair, who have formed a strong partnership since linking up last May.
Nicholls has already becoming Britain's leading women's doubles player and, after competing in her first final at WTA 1,000 level, will climb to a career-high 31st place in the world rankings.
