His time catching for Glenwood High School led to an athletic scholarship to play college baseball with the Georgia Bulldogs, which he turned down after the Baltimore Orioles selected him in the 1997 MLB Draft.

Werth signed a minor league contract with the Seattle Mariners in 2018 and played in 36 games for the Triple-A Tacoma Rainiers, but after a stint on the disabled list with a hamstring injury, he elected to retire from baseball.

[2] He began playing baseball competitively at the age of seven, and his youth team, the Springfield Flame, finished in third place at the 1993 Sandy Koufax World Series.

[8] Werth was expected to play for the Scottsdale Scorpions in the 1999 Arizona Fall League, but suffered a fractured left wrist in Bowie and was replaced by Tim DeCinces.

Rather than prematurely promoting him to Triple-A, farm system director Don Buford decided that Werth would begin the 2000 season in Bowie before making his MLB debut in 2001.

[8] On December 12, 2000, amidst a series of minor league trades, Werth was sent to the Toronto Blue Jays in exchange for left-handed pitcher John Bale.

[23] Although he packed a catcher's mitt upon his promotion to the majors, Werth's performance through his first 10 games with the Blue Jays, with multiple critical plays in right field, cemented his place as an outfielder.

[8] After completing spring training with the Blue Jays, Werth was traded to the Los Angeles Dodgers on March 31, 2004, in exchange for pitcher Jason Frasor.

[33] When he returned to the lineup, he made an immediate impact on the Dodgers' offensive performance, hitting a home run in his first game back before carrying a .450 batting average through the month of June.

[36] On October 2, his ninth-inning single set up Steve Finley's game-winning grand slam against the San Francisco Giants, a win that helped the team to clinch the National League (NL) West Division and send them to the playoffs for the first time since 1996.

At the start of November, he underwent a minor surgery to remove the synovial bursa in his inflamed knee, and he was expected to recover in full by spring training.

[44] Dodgers athletic trainer further believed that Werth had attempted to push his recovery time and had aggravated the scar tissue, causing it to inflame and induce further pain.

[45] That August, with still no improvement, Werth consulted with another doctor, Richard Berger of the Minnesota Mayo Clinic, who diagnosed him with a split tear of the ulnotriquetral ligament and performed an additional surgery to repair the wrist.

[47] On December 20, 2006, the Philadelphia Phillies, who performed a number of physical tests on Werth to confirm that he would remain healthy for the upcoming season, signed the player to a one-year, $850,000 contract, with additional incentives worth up to $1 million.

[48] Two days later, the Phillies traded Jeff Conine to the Cincinnati Reds to make room on the roster for Werth as a bench player, filling in for starters Pat Burrell, Aaron Rowand, or Shane Victorino as needed.

[44] Through August and September, Werth led the Phillies with a .340 batting average and .959 on-base plus slugging (OPS), and his 38 RBI were only one behind Philadelphia leader Ryan Howard.

As Burrell had recently become a free agent, the team had an interest in retaining Werth not just as an outfielder but as a right-handed power hitter in a predominantly left-handed lineup.

[68] Despite rumors that Matt Kemp would replace an injured Carlos Beltrán at the 2009 Major League Baseball All-Star Game, Werth instead filled that position in the NL outfield.

[69] On July 21, shortly after the All-Star break, Werth hit the first walk-off home run of his career in the bottom of the 13th inning to defeat the Cubs 5–1 and extend the Phillies' winning streak to 10 games.

[70] The Phillies clinched a playoff berth for the third consecutive season,[71] while Werth batted .268 and set career highs with 36 home runs, 99 RBI, 26 doubles, 91 walks, and 153 hits.

[66] Facing the Rockies once more in the 2009 NLDS, Werth made an early impression with a home run and a triple through Games 1 and 2, as well as a massive throw from right field to third base to stop Yorvit Torrealba.

[25] That changed during the NLCS, when Werth's 13th career postseason home run both set an NL record and helped lead the Phillies to a 4–2 victory over the San Francisco Giants in Game 5.

[92] He dismissed allegations of a slump, telling reporters that he was attempting to play through nagging shoulder and knee injuries and that he was consistently a stronger batter after the All-Star break.

Although the endpoint of Werth's home run was commemorated by a red seat at Nationals Park,[100] the Cardinals came back from a 6-0 deficit to win Game 5 by the score 9-7 and take the series from Washington.

[106] In the first month of the 2014 season, Werth led MLB with a 1.756 win probability added, a statistic measured by his 0.476 average in high-leverage situations, such as an eighth-inning grand slam against Marlins pitcher Carlos Marmol.

That January, he underwent surgery on his right shoulder to remove a necrotic bone and repair his acromioclavicular joint, with the expectation that he would start playing close to the beginning of the season.

[119] Still frustrated with his swing by mid-May, Werth spent most of a game against the Cardinals practicing in the batting cages, but he came off the bench for a pinch-hit grand slam, the second in Nationals history, en route to a 10–2 victory.

[25] The Nationals faced the Dodgers in the 2016 NLDS, where Werth hit his 15th career postseason home run in Game 3, tying Babe Ruth for 11th-most in MLB history.

[129] On March 27, 2018, the Seattle Mariners offered Werth a minor league contract as an "opportunity to extend his career" with the Triple-A Tacoma Rainiers.

He pled guilty again and was ordered to attend a diversion program and drug and alcohol screening, pay $1,600 in fines and fees, and his driver's license was suspended.