Betts and the World Series champion Boston Red Sox agreed to a $20 million, one-year contract on Friday, a $9.5 million raise that topped pitcher Max Scherzer's $8.8 million hike from Detroit in 2014.
Betts' standard didn't last the day, broken when deGrom and the New York Mets agreed at $17 million, a $9.6 million increase.
Cleveland shortstop Francisco Lindor, eligible for the first time, got an even bigger raise. His salary went up more than $9.9 million, from $643,200 to $10.55 million.
Davis and the Oakland Athletics reached a $16.5 million deal, a $6 million raise after he hit 48 home runs with a career-high 123 RBIs.
Arenado asked for a record $30 million in arbitration from Colorado and was offered $24 million. He will top the record for a salary for an arbitration-eligible player, a $23 million deal last year by Toronto and third baseman Josh Donaldson.
Among the 157 players eligible for arbitration at the start of the day, 142 reached deals on the busiest day of the offseason. All were for one year, though Milwaukee catcher Manny Pina's agreement included a team option for 2020.
There will be fewer hearings this winter than last year, when players won 12 of 22 cases argued - the most since 24 in 1990.
Washington reached an $18.8 million deal with third baseman Anthony Rendon, who got a $6.5 million raise, and Chicago White Sox slugger Jose Abreu agreed at $16 million, a raise of $3 million.
Boston also reached deals with shortstop Xander Bogaerts for $12 million and outfielder Jackie Bradley Jr. for $8.55 million.
Suspended shortstop Addison Russell and the Chicago Cubs agreed to a $3.4 million, one-year contract, a relatively small $200,000 raise for a player whose relationship with the team appeared strained after a domestic violence suspension.
Russell accepted a 40-game suspension last October for violating baseball's domestic violence policy following allegations made by his ex-wife. He missed the final 11 regular-season games plus the wild-card playoff loss and will be eligible to return May 3, barring postponements.
Russell will lose pay during the suspension. He can earn an additional $600,000 in roster bonuses if he is on the active roster for up to 150 days.
Cubs third baseman Kris Bryant agreed to a $12.9 million, one-year deal, a raise from $10.85 million.
Among the players still on track for hearings, Cole asked Houston for $13.5 million and was offered $11,425,000; and Trevor Bauer asked Cleveland for $13 million and was offered $11 million. Bauer won his hearing last winter.
Two first-time eligible starting pitchers didn't reach deals: Severino asked for $5.25 million and was offered $4.4 million by the New York Yankees, and Aaron Nola requested $6.75 million and was offered $4.45 million by Philadelphia.
Traded to Cincinnati by the Los Angeles Dodgers, Alex Wood asked the Reds for $9.65 million and was offered $8.7 million.
Hearings are scheduled for Jan. 28 to Feb. 15 in St. Petersburg, Florida. While many teams say they have a "file and trial" strategy for players who don't reach deals before the exchange, some of with pending cases may settle.
Some of the gaps are relatively modest: Washington outfielder Michael A. Taylor ($3.5 million vs. $3.25 million), Houston right-hander Chris Devenski ($1.65 million vs. $1.4 million) and Toronto right-hander Ryan Tepera ($1.8 million vs. $1,525,000)
Three of the remaining cases involve the Astros: shortstop Carlos Correa asked for $5 million and was offered $4.25 million.
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