SAN DIEGO -- The Padres have been one of the most active teams in the early stages of the undrafted free-agent market. General manager A.J. Preller hinted that might be the case last week, and he wasn't kidding.

"The system is strong," Preller said in his post-Draft press conference. "There's a lot of competition throughout the system. What we've talked to our group about is: It's got to be somebody that comes in and brings value -- either real performance value or somebody we feel like from a prospect standpoint can push somebody in the system."

• Team-by-team: Undrafted free agent signing tracker

The market for non-drafted free agents opened Sunday, and the Padres have already agreed with at least a half-dozen prospects, according to sources, though several of those signings are pending physicals. Per stipulations in this year's Draft, non-drafted free agents are capped at signing bonuses of $20,000.

Here's a rundown of San Diego’s early NDFA agreements, per sources. The Padres have not confirmed the deals.

Chase Walter, RHP, Western Carolina

Preller has always had a penchant for signing unproven pitchers with size in the mid-to-late rounds of the Draft. The event was only five rounds this year, so the tradition carried into the NDFA phase. Walter stands 6-foot-7 with a big-time fastball in the mid-90s. He complements it with a slider. The Padres' challenge will be helping Walter work through his control issues.

"Thank you @Padres for giving me the chance to continue the game I love. I can’t wait to start!" Walter tweeted on Sunday.

Carter Loewen, RHP, University of Hawaii

The Padres' Hawaiian pipeline is strong. Kirby Yates currently anchors the back end of the bullpen, and Joey Cantillo is one of the organization's fastest-rising prospects. Add Loewen to the mix. A 6-foot-4 reliever with a fastball in the mid-90s, Loewen posted a 3.18 ERA in 10 relief appearances in 2019. He was promoted to the role of closer in '20, just before the season was shut down due to COVID-19. Loewen owns a three-pitch mix (fastball/cutter/changeup) with a heater that sits at 92-94 mph.

Sam Ruta, SS, Pennsbury HS, Pennsylvania

Ruta was headed to Army before the Padres managed to pry him from his commitment. A 6-foot-2 lefty-hitting shortstop with a smooth stroke, Ruta might ultimately be ticketed for second or third base.

Zack Mathis, 2B, LSU

Mathis is a short, lefty-hitting second baseman with serious pop. That should remind Padres fans of another LSU Tiger -- Ryan Schimpf. Mathis spent his first two collegiate seasons playing junior college ball at San Joaquin Delta, where he batted .352 with 14 homers in 99 games.

Danny Denz, RHP, Memphis

Before his senior season was cut short, Denz posted a 1.50 ERA and struck out 26 batters in 18 innings. A 5-foot-9 left-hander, Denz struggled a bit with his control throughout college (though his walk rate was trending in the right direction toward the end of his career). He owns a fastball from 90-94 mph along with a curveball.

Michael Green, OF, Clemson

Green’s signing was reported by Baseball America and has not yet been confirmed by MLB.com. He played junior college ball before transferring to Clemson ahead of the 2019 season. The lefty-hitting corner outfielder spent a chunk of the year injured, but still posted a .307/.412/.475 slash line across 28 games.