With the last major of the season starting on August 31st in New York, the American has programmed a full run-up schedule: Washington last week, Montreal and Cincinnati still to come.
"Three tournaments is the perfect amount. I'd like to get as many matches as possible," the fifth seed said on a rainy Monday that saw the start of play delayed several hours with more afternoon rain interruptions.
"I'm the type of player, the more matches I play, the better I play, as long as my body can hold up," Shelton added.
"It's a great three-tournament run before having a week off leading up to the US Open. I'm just kind of going for it."
Among first-round matches completed, French veteran Gael Monfils opened his last Montreal campaign with a 6-4, 6-4 victory over Poland's Kamil Majchrzak.
Monfils, playing his final season on the ATP Tour, energised the rain-weary late-night crowd, winning four straight games to take a 5-2 lead in the second set.
He was broken in his first attempt to serve out the match but made no mistake on his second, advancing to a second-round meeting with 12th-seeded Learner Tien.
"I felt like I played well," Monfils said.
"I was serving really good, tried to be very accurate with my first serve and then second serve tried to be super aggressive and then use my forehand. I felt more and more I could hold his pace."
Monfils, coming off a first-round exit at Roland Garros, needed one hour and 38 minutes to dispatch Majchrzak, who won his first ATP title at s-Hertogenbosch in June.
Italy's former top 10 contender Matteo Berrettini, coming back from an abdominal injury, played his first match since Wimbledon and lost 6-3, 6-7(5), 6-3 to Argentine Mariano Navone.
The 12-day event is missing world number one Jannik Sinner and 24-time Grand Slam champion Novak Djokovic.
Roland Garros champion and Wimbledon finalist Alexander Zverev is the top seed ahead of Canadian Felix Auger-Aliassime.
Shelton, the ATP number 10 who reached last week's Washington quarters, is not bothered by the extra length of the tournament, which continues to spark criticism.
Shelton's best swing
"The two-week tournaments -- I think there's a lack of sustainability, for sure, but I don't know if there's a different way to go about it," he said.
"Jannik knows himself. Novak knows himself. Maybe I would do the same thing if I had won Wimbledon -- I didn't.
"It's tough to criticise those guys for the decisions that they make throughout the season when they're trying to sustain a level and maintain their health.
"At the same time, for me, this is one of my favourite parts of the year, one of my best swings, and I don't want to miss out on playing any of these tournaments."
Shelton said that he does not dwell on the 1,000 ranking points he needs to defend in Canada from his 2025 victory.
"If you're always thinking about defending or what week that you made points or didn't make points, it's easy to kind of get lost in your mind," he said.
"That's why I like to just think about my body of work for this year, 2026, what I'm doing and what I want to accomplish by the end of the year.
"To get another opportunity to be playing really good tennis leading into the US Open is kind of my main goal here.
"I'm looking forward to getting out there again."
