Thursday's Montreal semifinal pits Ben Shelton against Learner Tien on hard. Ben Shelton has won 4 in a row and 7 of the last 10 overall. Learner Tien has won 3 in a row and 6 of the last 10 overall.
The serve is where this match separates: Shelton has been winning 74.5% of first-serve points to Tien's 68%, and on hard that gap compounds fast. Shelton comes in off a compressed schedule; Tien comes in off a compressed schedule. A tiebreak or two would surprise nobody, with Shelton fractionally more likely to land the big points.