PHOENIX -- The Diamondbacks surprised the baseball world late Friday night by agreeing to terms with free-agent right-hander Corbin Burnes on a six-year, $210 million deal, sources told MLB.com.

The club has not confirmed the deal, which includes an opt-out clause after 2026 and is the richest in franchise history.

Burnes was regarded as the top free agent pitcher on the market this offseason after going 15-9 with a 2.92 ERA in 32 starts for the Orioles in 2024. What makes the move such a surprise is that while Burnes was linked to a handful of teams this offseason, the Diamondbacks were not seen as one of the contenders to sign him.

Starting pitching did not appear to be an area of need for the Diamondbacks, with returning starters Zac Gallen, Merrill Kelly, Eduardo Rodriguez, Brandon Pfaadt, Ryne Nelson and Jordan Montgomery all under contract for 2025.

The Diamondbacks’ surplus of starting pitching begs the question of whether the Burnes deal sets up the club to trade one of its other starters, potentially improving its payroll flexibility.

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Arizona entered last season with a franchise-record payroll, spending somewhere in the neighborhood of $170 million. The club had some money come off the books when free agent Christian Walker and designated hitters Joc Pederson and Randal Grichuk became free agents. Madison Bumgarner's five-year, $85 million deal also expired at the end of the 2024 season.

It's been no secret that Arizona had been looking to move Montgomery, who signed a one-year free-agent deal with a vesting player option for 2025. Montgomery, who was signed just after Opening Day, exercised his $22.5 million option following the 2024 regular season.

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Moving the money owed to Montgomery would help offset the amount coming to Burnes.

Either way, adding Burnes makes Arizona’s rotation one of the best in the game.

Injuries hampered the Diamondbacks’ starters in 2024, with Gallen, Kelly, Montgomery, Rodriguez and Nelson all missing time.

Burnes had 181 strikeouts in 194 1/3 innings over his 32 starts and was an All-Star for a fourth consecutive season. He ranked fourth in the American League in ERA -- behind only Triple Crown winner Tarik Skubal and the Astros duo of Ronel Blanco and Framber Valdez -- as well as third in innings pitched, tied for fifth in wins and tied for 10th in strikeouts.

The National League Cy Young Award winner with the Brewers in 2021, Burnes arrived in Baltimore in a blockbuster trade with the Brewers in February. Acquired to be the ace of a playoff contender, Burnes lived up to that billing with the O's.

Just as effective in the AL as he was in the NL, Burnes led the Orioles back to the playoffs as the AL's top Wild Card team. Although the O's were eliminated in the Wild Card Series by the Royals, Burnes was brilliant in his lone postseason start, throwing eight-plus innings of one-run baseball against Kansas City as Baltimore lost Game 1, 1-0.

Since becoming a full-time starter during the 2020 season, Burnes has been one of the most dominant aces in baseball.

In his four full seasons as a starter, Burnes has a 2.94 ERA and has averaged 215 strikeouts per season. He claimed the Major League ERA title in his Cy Young season with a 2.43 mark, and he won the NL strikeout crown with a career-best 243 K's in 2022, his second of three consecutive 200-plus-strikeout seasons.

Since 2021, Burnes ranks second in MLB with 858 strikeouts, behind only Dylan Cease (891). Among pitchers who have made at least 100 starts over that time, Burnes' 2.94 ERA is tied with Zack Wheeler for the second lowest, behind only Max Fried (2.87). Burnes also has the fourth-most innings pitched (757) of any starting pitcher since 2021, with only Aaron Nola (778 2/3), Logan Webb (761 1/3) and Wheeler (758 1/3) having thrown more.