The National Bank Open in Montreal enters its Round of 16 stage, and Sunday's featured matches promise compelling hard-court tennis. Three matchups bring a mix of ranking disparities and fresh rivalries, with no prior head-to-head history in two of the three pairings to add an element of the unknown.

Learner Tien vs. Thiago Agustin Tirante - Round of 16

Scheduled for approximately 5:00 PM EDT.

Tien (ranked 19) and Tirante (ranked 52) have never met before, making this a first encounter at the Round of 16 level. The ranking gap of 33 places gives Tien a clear edge on paper, though no odds are available to quantify the market's view. With no prior meetings to draw from, both players enter this matchup as unknowns to each other, and the higher-ranked Tien will look to assert his status as the more established top-20 presence.

Prediction: Learner Tien, based on ranking advantage.

Joao Fonseca vs. Ben Shelton - Round of 16

These two have met once before, with Shelton (ranked 5) defeating Fonseca (ranked 25) 6-3, 3-6, 6-3 in the Quarterfinal of the BMW Open in Munich. Shelton leads the head-to-head 1-0 and enters this Round of 16 matchup as the significantly higher-ranked player, sitting inside the top five. Fonseca did take a set in their prior meeting, showing he can compete, but Shelton closed out that match convincingly in three sets.

Prediction: Ben Shelton, based on ranking and existing head-to-head lead.

Botic Van De Zandschulp vs. Jakub Mensik - Round of 16

Van De Zandschulp (ranked 55) and Mensik (ranked 17) have no prior head-to-head history, making this Round of 16 clash a true first-time meeting. Mensik holds a considerable ranking advantage as a top-20 player facing an opponent ranked outside the top 50. No odds are available, but the 38-place ranking gap points clearly toward Mensik as the favorite.

Prediction: Jakub Mensik, based on ranking advantage.