SAN DIEGO -- All season long, prospects from the Padres' top-ranked farm system have arrived in San Diego. The biggest name yet arrives Tuesday night.
Luis Urias, San Diego's presumed second baseman of the future, has been promoted from Triple-A El Paso before Tuesday's game against the Mariners.
Urias, 21, is ranked No. 22 on MLB Pipeline's Top 100 prospects list and No. 4 in the Padres' system. He's hitting .296/.398/.447 this season with eight home runs in 120 games this season for El Paso.
The club placed left-hander Clayton Richard (left knee inflammation) on 10-day disabled list.
After signing out of Mexico in December 2013 at 16 years old, Urias has moved quickly through the San Diego farm system. The Padres haven't announced their specific plans for Urias over the season's final month, but he's expected to see regular playing time.
Though Urias is capable of playing shortstop, most of that playing time will come at second base -- where the combination of Jose Pirela, Cory Spangenberg and Carlos Asuaje (who was demoted to Triple-A) has struggled this season. The Padres' -0.9 combined fWAR at second is the worst mark in the Majors.
Urias' most important skill might be his ability to reach base. In five Minor League seasons, he's compiled a .397 on-base percentage, which could prove crucial on a Padres team that's finished last in the Majors in OBP in each of the past four seasons. (They currently sit 29th at .298.)

MILB Video - Title: Urias triples for third hit - Url: http://www.milb.com/r/video?content_id=2402961383

Urias' hit tool is recognized as one of the best in the Minor Leagues, though he doesn't boast much power. His defense is also well above average.
Urias is the latest, and by far the most noteworthy, callup in a season full of them for San Diego. Four rookies -- Joey Lucchesi, Eric Lauer, Brett Kennedy and Jacob Nix -- could all make starts this week (should Lauer return from his forearm strain as expected). Outfielder Franmil Reyes and relievers Robert Stock, Trey Wingenter and Jose Castillo have also debuted.
Shortstop Fernando Tatis Jr., San Diego's top prospect, is out for the season with a broken bone in his left thumb. The Padres envision Tatis and Urias as their double-play duo of the future, but they won't take the field together until 2019 at the earliest.
Still, it's likely the Padres promote catcher Francisco Mejia at some point in September. Mejia, acquired from Cleveland on July 20 for relievers Brad Hand and Adam Cimber, is baseball's No. 21 ranked prospect according to MLB Pipeline. He entered Monday hitting .300/.343/.480 in 26 games since joining El Paso.
For now, it's Urias' time. Presuming he's in the starting lineup Tuesday, he'll face six-time All-Star and former American League Cy Young Award winner Felix Hernandez. Welcome to the show.