His dad, Tom, wore No. 20 in his first three big league seasons pitching for the Montreal Expos in the 1970s. But it was off limits during Neil's seven seasons with the Pittsburgh Pirates because it was retired in 1972 in honor of Hall of Famer Pie Traynor.
Six days after his trade to New York, Walker was in a No. 20 jersey Tuesday for the NL champions' holiday party at Citi Field.
''I never had an opportunity to wear it in Pittsburgh,'' the second baseman said. ''Be proudly wearing it here in New York.''
Walker spoke at the ballpark with manager Terry Collins and said he had phone conversations with general manager Sandy Alderson and captain David Wright. Walker and free-agent shortstop Asdrubal Cabrera, who agreed last week to an $18.5 million, two-year contract, will be in the middle of the Mets' new-look infield.
''It's really impressive. It's something that is kind of similar to what was going on in Pittsburgh a few years ago with a lot of young guys and some good veterans in the clubhouse,'' said Walker, who wore Nos. 19 and 18 in Pittsburgh. ''There's nobody that has better pitching than this staff right here.''
Selected by Pittsburgh with the 11th overall pick of the 2004 amateur draft, Walker knew a trade was possible. He is eligible for free agency after next season.
Like Cabrera a switch-hitter, Walker takes over at second base from postseason star Daniel Murphy, who became a free agent and turned down the Mets' $15.8 million qualifying offer.
''We had to make a decision, not knowing where we were going to go with Murph,'' Collins said. ''You're talking about the middle of the infield being veteran guys that know the game, know how to play, that have track records, know what it takes to be successful.''
With the departure of Niese, Collins hopes the Mets can re-sign 42-year-old Bartolo Colon to join a rotation that includes Matt Harvey, Jacob deGrom, Noah Syndergaard and Matz. Zack Wheeler is expected back from Tommy John surgery by the summer.
''I know there's talks with him going on,'' Collins said. ''We told him, `Look, there may be a starting spot for you early in the season.' So I hope they can get something done.''
Collins said Wright, limited to 38 regular-season games this year because of a hamstring injury and spinal stenosis, was in California ''finding out what he has to do for the rest of the winter to get himself ready.''
''I think it's a little early to sit down with him and say, hey, we want you to play 135 games,'' Collins said. ''I just think that's unfair at this particular stage until we know how he comes out of the winter.''
Collins was proud of outfielder Michael Cuddyer's decision to retire. Owed $12.5 million next year, Cuddyer instructed the players' association to reach a settlement with the Mets.
''You talk about a true professional, this guy knew when it's time,'' Collins said. ''The respect he has for the game of baseball, he said, hey, it's time to get out. A lot of guys would not have done it. They would have gone to spring training and had to sit for time on the DL and collect that money.''
NOTES: LHP Jerry Blevins agreed to a one-year contract that guarantees $4 million and allows him to earn an additional $1 million in performance bonuses. The 32-year-old left-hander was acquired from Washington on March 30 and appeared in seven games, retiring all 15 batters he faced - all but one a left-handed hitter. He broke his left forearm when struck by a line drive off the bat of Miami's Dee Gordon on April 19, then broke it again on Aug. 3 when he slipped off a curb in Port St. Lucie, Florida. Blevins would earn $150,000 each for 40 and 45 relief appearances, $200,000 for 50 and $250,000 apiece for 55 and 60. He is changing uniform numbers. ''Dear Santa: You can give my (hash)13 to Asdrubal Cabrera,'' Blevins tweeted. ''He signed with the (at)Mets first. I will figure out what number to wear.''