Per MLB Network's Jon Heyman, the Phillies' proposal is believed to be worth around $110 million.
After a slow free-agent period, MLB teams are starting to kick things into gear with less than one month before pitchers and catchers will report to spring training.
Realmuto, DJ LeMahieu and George Springer were widely regarded as the top position players available this offseason. LeMahieu reportedly agreed to a six-year, $90 million deal to stay with the New York Yankees, per ESPN's Jeff Passan.
On Tuesday, Heyman reported that Springer agreed to a six-year, $150 million deal with the Toronto Blue Jays.
Jayson Stark of The Athletic reported last week the Phillies made a five-year proposal worth "slightly north of $100 million" to Realmuto. It's unclear if Wednesday's report is about that same offer or a potentially new one as the two sides continue to negotiate.
Realmuto has spent the past two seasons in Philadelphia after being acquired in a February 2019 trade with the Miami Marlins. The 29-year-old has hit .273/.333/.492 with 36 homers and 115 RBI in 192 games with the Phillies.