"We are not able to confirm any news regarding Robinson Cano at this time," the Mariners said in a statement. "If and when an agreement is completed and finalized, we will announce."
The report originally came from Cano's camp through ESPN Deportes reporter Enrique Rojas, who also said that Cano is to undergo a physical in Seattle on Monday.
The Mariners, like most Major League clubs, don't confirm contract negotiations until physicals are completed and a contract is officially signed, which often takes several days. Thus, official word of Cano's signing shouldn't be expected until sometime during the Winter Meetings, which will take place Monday through Thursday in Lake Buena Vista, Fla.
But Mariners players are already celebrating the addition and anticipating more to come from general manager Jack Zduriencik as the club still has more payroll available.
"I think this is just the start," said outfielder Michael Saunders, one of Seattle's core of young players. "It's no secret that it's been tough to get free agents to come to Seattle, but hopefully this opens the floodgates and shows others we're ready to win and it can start a trend. It obviously shows how serious Seattle is about winning a championship."
Zduriencik pursued free agents Prince Fielder in 2011 and Josh Hamilton last year without success, but this time, he came up with a deal that will add a slugging left-handed hitter to a young team looking to compete in the tough American League West.
The contract terms, if accurate, would equal Albert Pujols' current deal with the Angels for the third-largest contract in MLB history.
Alex Rodriguez signed a 10-year deal for $252 million with the Rangers in 2001, then reworked another 10-year, $275 million contract with the Yankees in 2008. Pujols signed with the Angels for $240 million over 10 years in 2012.
Cano, 31, has been regarded as the premier free agent in this year's market and is coming off a season in which he hit .314 with 27 home runs and 107 RBIs in 160 games for the Yankees.
Cano and his representatives flew to Seattle on Thursday and met with Mariners officials past midnight, looking for a better deal than the seven years for about $170 million offered by the Yankees.
Early Friday morning, a report by the New York Daily News said that talks between Cano and the Mariners had broken down when his agent, Jay-Z, raised the free agent's asking price.
But Cano wound up agreeing to a deal that dwarfs even the seven-year, $175 million contract the Mariners gave ace pitcher Felix Hernandez last spring, which at the time made him the highest-paid pitcher in Major League history.
Cano has been one of the most consistent offensive performers in the Major Leagues since 2009, averaging 28 home runs and 103 RBIs per season during that time. He's been an American League All-Star and finished in the top six in AL Most Valuable Player voting in each of the past four seasons and this year completed a contract that paid him $15 million for 2013.
The Mariners have considerable payroll available this offseason, with only Hernandez ($22 million) and fellow pitcher Hisashi Iwakuma ($6.5 million) under any sort of sizable contracts and just two players -- outfielder Michael Saunders and first baseman Justin Smoak -- entering the arbitration process.
Hernandez is the only returning player currently under contract beyond 2014 on a Seattle club whose payroll has been in the $90 million range the past few years. Iwakuma has a $7 million option for 2015 and the club signed free-agent utility man Willie Bloomquist to a two-year, $5.8 million deal this week, but the Mariners otherwise have a roster filled primarily with younger, controlled-cost players.
Rookie Nick Franklin was the Mariners starting second baseman for the final four months last season, batting .225 with 12 home runs and 45 RBIs in 102 games after replacing Dustin Ackley.
Ackley moved to the outfield and likely will stay there now, with Cano presumably entrenched as the second baseman for new manager Lloyd McClendon.
The Mariners are looking to upgrade an offense that was second in the AL in home runs this year but was 12th in scoring and last in batting average as the club went 71-91. Seattle finished the season having used seven starting position players aged 26 or younger.
Cano brings an impact bat to the middle of the order, but Seattle still needs to find a designated hitter after Kendrys Morales rejected a $14.1 million qualifying offer. Zduriencik also is pursuing outfield help and another pitcher for a rotation topped by Hernandez and Iwakuma, two of the AL's premier starters.
Safeco Field is a notorious pitcher's park, though the fences were moved in last season. But the park favors left-handers and Cano has fared well in Seattle, putting together a .309/.350/.487 line in 163 plate appearances, with four home runs and 20 RBIs, in 40 games. That isn't far off his Yankee Stadium line of .312/.368/.517 in 401 games.
Cano was extended a qualifying offer by the Yankees, which means any team that signs him would surrender a first-round choice in next year's First-Year Player Draft unless it is in the first 10 protected slots. The Mariners hold pick No. 6, so they would instead give up their next selection, which currently would be the 31st choice if the Mariners receive compensation for Morales signing elsewhere.
If Seattle retains Morales, its second choice would be the sixth pick in the second round. Regardless of any further movement, the Yankees will receive a compensatory pick at the end of the first round for losing Cano.