Daisuke Matsuzaka says he still has something to prove.
Koji Uehara wants to help his former team regain its past glory.
The two former U.S. major leaguers are among several Japanese stars that will be looking to extend their careers back home when the country's professional league opens on Friday.
After an injury-filled stint last season with the Softbank Hawks of the Pacific League, the 37-year-old Matsuzaka has signed with the Chunichi Dragons of the Central League.
"Because I've not been able to pitch these past years, I want to really demonstrate that I can pitch and am fit," Matsuzaka said.
In a career that has included a World Series championship with the Boston Red Sox in 2007 and two World Baseball Classic most valuable player awards (2006, 2009), Matsuzaka is preparing for his 20th professional season.
Matsuzaka returned from the majors in 2015, but had right shoulder surgery that year and made just one appearance for the Hawks from 2015 to 2017.
In his most recent exhibition game, he gave up three runs on six hits in a 6-3 loss to the Lotte Marines. But he has shown flashes of his former dominance, and Chunichi fans are hoping he can contribute to a team that finished out of the playoffs last season.
Uehara signed with his former team, the Yomiuri Giants. The 42-year-old right-handed closer spent nine seasons in Major League Baseball, compiling 95 saves and a 2.66 ERA. He played last season with Cubs.
Before he left for the majors, where he helped the Red Sox win the World Series in 2013, Uehara was the ace of the Giants pitching staff, leading the team to the championship in 2000 and 2002.
Since his departure, the Giants have struggled to maintain their reputation as Japan's oldest and most successful team.
They missed the playoffs last season and have been rocked by a series of embarrassing scandals off the field.
In 2015, it was discovered that three Yomiuri pitchers gambled on games with underworld bookmakers.
"I want to do my best to contribute to wins that will move us toward a championship," Uehara told reporters. "Other Japanese clubs showed interest, but the Giants had the most positive approach, and I am grateful."
While some former major leaguers from Japan balk at the chance to return to Nippon Professional Baseball, others have returned successfully and extended their careers.
Outfielder Kosuke Fukudome, after five seasons in the majors with the Chicago Cubs, Cleveland Indians and Chicago White Sox, is now in his sixth season with the Hanshin Tigers.
Tadahito Iguchi, who won a World Series with the White Sox, is starting his first season as manager of Chiba Lotte after closing out his playing career with the Marines.
Elsewhere, outfielder Norichika Aoki has returned to his former team, the Yakult Swallows.
The 36-year-old played for Yakult from 2004 to 2011, winning the Central League batting title three times before going to the majors after the 2011 season.
Aoki started his major league career with the Milwaukee Brewers in 2012, and also played for the Kansas City Royals, San Francisco Giants, Seattle Mariners, Houston Astros, Toronto Blue Jays and New York Mets.
Over six years in the majors he had a batting average of .285 with 774 hits and 98 stolen bases in 758 games.