SAN DIEGO -- The Padres have taken to using metaphors when they refer to the prospects in their loaded, top-ranked farm system.
"Hot talent lava."
"Waves of talent."
Whatever the geologic trope, the point is this: There's a lot of young talent in the organization. And it's going to arrive en masse over the next few seasons.
Francisco Mejia -- the top-ranked catching prospect according to MLB Pipeline and No. 21 overall -- is the latest to join the fray.
Mejia, 22, was promoted from Triple-A El Paso ahead of Tuesday's game in Arizona. He made his Padres debut when he pinch-hit and struck out during the sixth inning of a 6-0 loss to the D-backs. He is expected to receive his first start on Thursday in Cincinnati after an off-day Wednesday.
Mejia came to the Padres in July in the deal that sent relievers Brad Hand and Adam Cimber to Cleveland. He's been on fire since, batting .328/.364/.582 with seven homers in 31 games for Triple-A El Paso (whose regular season ended Monday).
That's merely a continuation of the rest of Mejia's Minor League career. His claim to fame is a 50-game hitting streak during the 2016 season. He batted .293 in six Minor League seasons.
"He's hit everywhere he's been his entire life," Padres manager Andy Green said. "He's got unique bat-to-ball skills and an ability to put all sorts of pitches in play."
In 18 big league plate appearances for Cleveland over two seasons, Mejia tallied two hits and three walks. He's yet to hit his first home run.

Of course, the Padres already have an effective catcher in Austin Hedges, who has posted a .714 OPS this season while serving as one of the best behind the plate. The Padres have played Hedges on a near-everyday basis over the past month, knowing that Mejia would be arriving to ease the workload in September.
"There's room for two back there to be a great baseball team," Green said. "You're probably looking at split time through the month of September."
That's the short-term view. Hedges was the game's top catching prospect not long ago, and he just turned 26. It's worth wondering whether there's actually room for both next season and beyond, as the Padres look to open their window for contention in the National League West.
But there's a ready-made solution if San Diego wants to keep both. Mejia spent time at third base and in the outfield in the Indians' organization. The Padres felt as though the push toward versatility stunted Mejia's growth as a catcher. They shifted him behind the plate full-time upon his arrival in El Paso.
"His catching became second fiddle to his ability to play left field," Green said. "We're not looking to do that with him at this point in time. That doesn't mean that in the future we won't ask him to bounce around the field. That might happen."
"It would always depend on the situation," Mejia said. "But I got a lot of reps in the outfield. … Given the situation, if that's what they needed, then I know I could do it."
Mejia's versatility could allow the Padres to use both him and Hedges in the same lineup on certain days. On others, Mejia's presence should ease the burden on Hedges, at the sport's most demanding position.
Hedges has made it clear he doesn't feel burdened by the workload, and he'd prefer to rank among the MLB leaders in games caught. But he's also open to splitting time with Mejia.
"I believe in this team, and I want this team to win," Hedges said. "Whatever that takes, I'm going to support anything that happens. Given that, I want to play every day. I want to play 130, 140 games, and I'll make that very clear.
"Whether that means he's catching the other ones and playing another position, or if our best way of winning is something else, then I'll be for that, too. But I believe in my abilities in myself being an everyday catcher."
As for the rest of the system, the Padres have nine players ranked in MLB Pipeline's Top 100 Prospects -- the most in baseball. Second baseman Luis Urias (No. 22) was promoted last week.
Shortstop Fernando Tatis Jr. (No. 2) is out for the year with a broken bone in his left thumb, but he'll probably arrive sometime early next year. Starters Chris Paddack (No. 48) and Logan Allen (No. 85) are expected next season as well.
Behind them, lefty MacKenzie Gore (No. 11), lefty Adrian Morejon (No. 49), righty Michel Baez (No. 60) and lefty Ryan Weathers (No. 99) are on the horizon, with a handful of others in a system that's widely believed to be as deep as it is top-heavy.
The waves (or lava) aren't going to stop anytime soon.