The Cincinnati Reds continued their busy offseason, matching the biggest free-agent contract in team history by agreeing to a four-year, $64 million deal with outfielder Nick Castellanos, sources confirmed to ESPN's Jeff Passan on Monday.

The deal has an opt-out clause after the first season, sources said.

Castellanos, who undoubtedly made some money for himself after his midseason trade from the Detroit Tigers to the Chicago Cubs, continued to be a doubles machine, with 58 between the two teams in 2019.

He has averaged 38 doubles in his six full seasons in the majors.

His power increased last season as well. After hitting 11 home runs in 403 at-bats for Detroit, Castellanos hit 16 with the Cubs in just 212 at-bats. His OPS+ of 151 in 2019 was easily the best of his career.

Castellanos' deal matches the one the Reds gave to infielder Mike Moustakas this offseason. They will be tied as the second-highest-paid players on the roster behind Joey Votto, who makes $25 million each of the next four seasons.

Moustakas hit .254 with 35 homers and 87 RBIs last season and made the All-Star team for the third time.

Left-hander Wade Miley agreed to a two-year, $15 million contract with the Reds in December. The deal includes a club option for 2022 that, if exercised, can bring the total value to $24 million.

Miley, 33, went 14-6 with a 3.98 ERA and 140 strikeouts for the Houston Astros during the regular season, but he tailed off badly down the stretch and -- after making just one appearance during the American League Division Series -- was left off the rosters for both the AL Championship Series and the World Series.

In early January, Cincinnati signed Japanese outfielder Shogo Akiyama to a three-year, $21 million contract.

Akiyama, 31, has played parts of nine seasons for the Seibu Lions of the Japanese Pacific League. The left-handed-hitting Akiyama batted .303 with 20 home runs and 62 RBIs in 143 games for Seibu last season.

Castellanos joins a crowded outfield that will get sorted out in spring training.

Akiyama was a five-time All-Star center fielder for Seibu but could move to a corner spot. The Reds already have center fielder Nick Senzel, who is recovering from shoulder surgery.

Aristides Aquino took over in right field last season after Yasiel Puig was traded to Cleveland and had a sensational debut, but he slumped as the season closed out. The Reds also have Jesse Winker and Phillip Ervin.

Drafted in the first round by Detroit in 2010, Castellanos, who turns 28 in March, has mostly played in obscurity. The Tigers made the postseason in 2014 but haven't sniffed October since. After joining the Cubs, Castellanos was praised for the energy and hunger he brought to a team that was going in the wrong direction.

"He hasn't won in a few years, so I completely understand that," former teammate Ian Happ said. "What I see is just the joy of the game. Playing like a little kid. Enjoying a new team. That's what it looks like."

Upon joining the Cubs, Castellanos famously said that "every day is like Opening Day."

His defense hasn't rated as well as his offense, but he showed no issues in a difficult right field at Wrigley, though he profiles more in left. His big strength on offense is finding the gaps in left-center and right-center.

For his career, Castellanos is a .277 hitter with 120 home runs and 460 RBIs.

The Reds haven't been to the playoffs since 2013, when they won 90 games and lost to the Pirates in the National League wild-card game. Cincinnati then launched into a rebuild, trading stars for prospects. The team lost at least 94 games annually from 2015 to 2018.

The Reds decided to try to become competitive again last season and acquired Puig, Matt Kemp, Alex Wood, Tanner Roark and Sonny Gray, who became an All-Star. Puig, Kemp and Roark were dealt during the season. Cincinnati finally escaped last place, finishing ahead of Pittsburgh with a 75-87 mark, and wasted a lot of solid pitching along the way.

With Castellanos heading to Cincinnati, Josh Donaldson to Minnesota and Marcell Ozuna to Atlanta, the top free agents are now all signed. Puig and utility man Brock Holt are likely the top free agents remaining.

ESPN's Jesse Rogers and The Associated Press contributed to this report.