In 2013, he led the organization in hits for the second consecutive year, and Baseball America designated him the "Best Hitter for Average" among the Blue Jays' prospects.

In 2015, Pillar led all major league outfielders in putouts, and was named the Wilson Defensive Player of the Year for center field.

[4][5][6] In 2016 he established the Pillar-Lambert Scholarship in Accounting at Tel Aviv University in Israel, in honor of his late maternal grandfather Ed Lambert.

[10] In high school at Chaminade College Prep, Pillar moved from the infield to the outfield in his junior year for the baseball team.

[14] He majored in and graduated with a degree in mathematics and business, and played center field for the Toros baseball team, for which he was an All-American.

[24] When he was promoted to the majors two years later, Blue Jays general manager Alex Anthopoulos said: "Clearly ... and I say that respectfully, we got him wrong.

[37] He was considered one of the most consistent hitters and defenders in the Eastern League, "with great instincts, a powerful and accurate throwing arm," and showed speed on the base paths.

[41] In 123 games between New Hampshire and Buffalo, he had 39 doubles and 155 hits which, at the time of his August 2013 promotion, were the second- and third-highest totals, respectively, in the minor leagues.

[5][24][50][51] Pillar was called up to the Blue Jays for the first time in his career on August 14, 2013, after center fielder Colby Rasmus was placed on the 15-day disabled list and utility player Emilio Bonifacio was traded to the Kansas City Royals.

[54][55] General manager Alex Anthopoulos stated that, at the time of his call-up, he considered Pillar a "legit center option".

On August 24, Pillar hit his first career home run, a three-run shot off Houston Astros starter Brad Peacock.

[61][62] On June 9, Pillar hit a walk-off single, scoring Erik Kratz to give the Blue Jays a 5–4 win over the Minnesota Twins.

[63] On June 24 he was sent back down to Buffalo for throwing his bat after manager John Gibbons removed him for pinch hitter Anthony Gose.

[65] In the 2015 offseason, the Blue Jays acquired Michael Saunders from the Seattle Mariners, and Pillar was expected to compete for the fourth outfielder role heading into spring training.

Pillar made several highlight reel catches throughout the season, including scaling the left field wall to rob Tim Beckham of a home run on April 15.

[66] Blue Jays fans voted it the play of the year and Pillar called the catch a "life-changing moment" that brought him from obscurity to prominence in Toronto and around the league.

[72] Pillar played in all 5 games of the 2015 American League Division Series against the Texas Rangers, and batted .333 with 1 home run and 4 RBIs.

[74] Pillar opened the season as the Blue Jays' lead-off hitter, but struggled, hitting .188 with no walks through April 16, and was moved down in the order by manager John Gibbons.

[14] Pillar was named as a finalist for the Gold Glove Award in center field, along with Jackie Bradley Jr. and Kevin Kiermaier.

The following day, Pillar hit the first walk-off home run of his career, a solo shot off Mariners closer Edwin Díaz to give Toronto a 3–2 victory.

[86] In Toronto's 5–3 victory over the New York Yankees on March 31, Pillar became the first Blue Jay to steal three bases in one inning, when he stole second, third, and home plate in the eighth.

[88][89] He was placed on the disabled list on July 15 after spraining his right sternoclavicular joint (where his collarbone attaches to his chest wall) on a diving catch.

[90] Pillar finished the 2018 season leading the team in batting average (.252), doubles (40; a career high), and stolen bases (14), while coming in 10th in the American League in stolen-base percentage (83.25%).

[91][37] With the team trading pitcher Aaron Loup during the season, Pillar became – at 29 years of age – the longest-tenured active Blue Jay.

[95] On April 2, 2019, the Blue Jays traded Pillar to the San Francisco Giants for Alen Hanson, Derek Law, and Juan De Paula.

[97] On May 4, Pillar earned an MLB Play of the Week award catching Nick Senzel's would-be home run by scaling the center field wall.

[98] Pillar assumed the position of everyday center fielder, as Steven Duggar's continued injury problems forced him into a few stints on the injured list.

[110] On May 17, Pillar was struck in the face by a 94 miles per hour (151 km/h) fastball thrown by Atlanta Braves pitcher Jacob Webb in a game at Truist Park, with the bases loaded, forcing in a run.

[120] He worked his way back post-surgery, and played in six minor league rehab games at the end of September, batting 7-for-22 with a home run and six RBIs.

[122] On February 2, 2024, Pillar signed a minor league contract with the Chicago White Sox, and was a non-roster invitee to spring training.