None of the trio dropped a set in their quarter-final clashes, with Nakashima beating Luciano Darderi 6-2 6-3, before Jodar defeated Arthur Fils 7-6 (7-5) 6-3 on Tuesday (Wednesday AEST).
Nakashima sent down 11 aces and offered up a subdued celebration for the career-breakthrough win in Montreal.
He will meet Jodar for a place in the final after the Spaniard extended his breakthrough season with a 34th win of the year.
The 28th-seeded Nakashima converted a break point in the fourth game before breaking his opponent to love to close out the first set, as the visibly frustrated Darderi's composure unravelled.
Darderi dug in his heels in the second set but could only hold off the determined Nakashima for so long, as the American broke him in the penultimate game.
Nakashima sent the 19th-seeded Italian skittering around the court in the final game, forcing him into an error at the net on match point and pumping his fists in celebration after the customary post-match handshake.
Jodar extended his remarkable first season on tour with a composed win over Fils, taking the opener in a tiebreak after a rain delay.
He carried that momentum into the second set, breaking three more times to secure the victory that will lift him to at least No.11 in the rankings.
"I played a very high level against a tough player like Arthur," the 19-year-old said in his post-match on-court interview.
"I had to give my best to win this match. It worked perfectly, staying calm in those important moments of the match, those pressure moments."
Ben Shelton produced one of the standout performances of his career, overpowering Jakub Mensik 6-3 6-1 to set up a last-four clash with fellow American Tien as momentum builds ahead of the US Open.
After a near-flawless opening set, the hard-serving Shelton fired a backhand winner down the line to break the Czech for a 2-0 lead in the second, punctuating the moment with a thunderous roar.
The 23-year-old sealed the 72-minute win when an overwhelmed Mensik sent a backhand long on match point.
"It was a great performance, super happy with that one," Shelton told the Tennis Channel.
He'll next face Tien after the 12th-seeded teenager's 6-3 6-2 victory over Spain's Daniel Merida.
With PA.
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