He played in Major League Baseball (MLB) for the Florida Marlins, Chicago White Sox, Detroit Tigers, Colorado Rockies, Pittsburgh Pirates, Los Angeles Angels of Anaheim, Atlanta Braves, Toronto Blue Jays, and Texas Rangers.

Taken as the fourth overall selection of the 1997 MLB draft by the San Francisco Giants, Grilli was one of the top starting pitcher prospects in all of Minor League Baseball, ranked 54th in 1998 and 44th in 1999.

[1] Although born in Michigan, Grilli moved to Central New York when his father, Steve, played for the Syracuse Chiefs beginning in 1978.

[4] In his junior year, Grilli struck out 18 batters in a game to break Charles Nagy's Big East Conference record.

[7] The San Francisco Giants selected Grilli in the first round, fourth overall, of the 1997 Major League Baseball draft.

[6] Grilli earned high reviews from scouts before the draft, who noted his good delivery, size and bloodlines.

[10] On July 25, 1999, the Giants traded Grilli and Nate Bump to the Florida Marlins to acquire Liván Hernández.

In January 2005, after the White Sox signed Tadahito Iguchi, Grilli was designated for assignment and eventually released.

Tigers scouts and GM Dave Dombrowski were familiar with his abilities, having previously traded for him while running the Marlins in 1999.

After helping the Triple-A affiliate Toledo Mud Hens to the International League Championship (he clinched the deciding game), Grilli joined the parent club for a brief late-season audition.

He also had a good spring training and earned a spot in the Tigers bullpen as a long reliever, leading to his first extended stint in the majors.

In 2007, Grilli posted career highs in almost every category, including games (57), innings (792⁄3), strikeouts (62), wins (5), and holds (11).

Tigers teammate Jeremy Bonderman, known for throwing a very effective slider,[18] helped Grilli tweak his grip and delivery.

[24] Grilli suffered a severe knee injury in spring training while running sprints and would later undergo surgery for a torn quadriceps muscle.

[33] Just two weeks later, the Pirates made a major trade by sending incumbent closer Joel Hanrahan along with infielder Brock Holt to the Boston Red Sox for infielder Iván DeJesús Jr., relief pitcher Mark Melancon, relief pitcher Stolmy Pimentel and outfielder Jerry Sands.

Jason Grilli tied Jim Johnson of the Baltimore Orioles, Sergio Romo of the San Francisco Giants and Mariano Rivera of the New York Yankees for the most saves in the MLB that month.

Grilli pitched a scoreless ninth inning in the Pirates win over the Cincinnati Reds in the 2013 National League Wild Card Game.

[45][46] Grilli's original intended role was to serve as Craig Kimbrel's setup man in the eighth inning of games.

[49] On July 11, in a game against the Colorado Rockies, Grilli was covering first base on a ground ball when he tripped and ruptured his left Achilles, causing him to miss the rest of the season.

[55] In a June 3, 2017 game against the New York Yankees, Grilli gave up four home runs in a single inning of relief, becoming the first Blue Jays reliever to do so.

[59] He is the son of former major-league pitcher Steve Grilli,[60] who pitched for parts of four seasons in the late 1970s, including three with the Detroit Tigers.

His father is also known for being the losing pitcher for the Rochester Red Wings in the longest professional baseball game on June 23, 1981.

[62] Nearly one year after the trade, Grilli made his first appearance back at PNC Park, as a member of the Atlanta Braves.