Major League Baseball recommended teams have protective netting between the dugouts for any field-level seats within 70 feet of home plate.

The guidelines were announced Wednesday at the winter meetings in Nashville, Tennessee, following a season in which several fans were injured by foul balls, prompting MLB to study fan safety. Most teams are expected to expand their use of netting.

“It is important that fans have the option to sit behind protective netting or in other areas of the ballpark where foul balls and bats are less likely to enter,” commissioner Rob Manfred said in a statement.

Boston, the Los Angeles Dodgers and Philadelphia immediately said they will follow the recommendation. Cincinnati and Houston said their ballparks already are in compliance.

More deals: The National League champion New York Mets filled a key spot by obtaining second baseman Neil Walker from Pittsburgh for pitcher Jon Niese, and the Detroit Tigers bolstered their bullpen by acquiring reliever Justin Wilson from the New York Yankees.

The Arizona Diamondbacks, meanwhile, kept upgrading their rotation. A day after finalizing a $206.5 million deal for big league ERA leader Zack Greinke, they announced their five-player trade with Atlanta that brought All-Star right-hander Shelby Miller and sent No. 1 draft pick Dansby Swanson to the Braves.

Miller should slot into the No. 2 spot in the rotation ahead of Patrick Corbin, Rubby De La Rosa and Robbie Ray.

Other teams are waiting for the market to develop, especially for hitters.

Among the 17 elite free agents who didn’t accept qualifying offers, five have reached agreements and all are pitchers: Greinke, Jordan Zimmermann, Jeff Samardzija, John Lackey and Marco Estrada. In addition, Hisashi Iwakuma has an agreement with the Los Angeles Dodgers that remains to be finalized.

Among the remaining 11 are pitchers Wei-Yin Chen, Yovani Gallardo and Ian Kennedy, joined by first baseman Chris Davis; second basemen Daniel Murphy and Howie Kendrick; shortstop Ian Desmond; and outfielders Jason Heyward, Justin Upton, Alex Gordon and Dexter Fowler.

In another trade, Seattle obtained first baseman Adam Lind from Milwaukee for right-handers Daniel Missaki, Carlos Herrera and Freddy Peralta.

The Mets got Walker a day after their No. 1 choice for a new second baseman, Ben Zobrist, signed as a free agent with the Chicago Cubs.

Walker fills the hole created when Murphy became a free agent after New York lost the World Series. Walker batted .269 with 16 homers and 71 RBIs this year.

Niese became expendable with the development of young Mets aces Jacob deGrom, Matt Harvey, Noah Syndergaard and Steven Matz. Niese was 9-10 with a 4.13 ERA last season. A starter for years, he was shifted to the bullpen for the postseason.

The Yankees dealt Wilson to Detroit for two minor league pitchers. Earlier this offseason, the Tigers acquired closer Francisco Rodriguez and right-hander Mark Lowe.

Yankees general manager Brian Cashman is willing to trade left fielder Brett Gardner and closer Andrew Miller. Cashman is confident Dellin Betances could take over as closer.

Second baseman Chase Utley completed his one-year deal to remain with the Los Angeles Dodgers.

Former A’s outfielder Craig Gentry and the Los Angeles Angels reportedly have agreed to a $1 million, one-year contract. Gentry split time with the A’s and Triple-A Nashville this year.