This story was excerpted from AJ Cassavell¡¯s Padres Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

The Padres have never been shy about challenging Ethan Salas, their 18-year-old top prospect and MLB Pipeline's No. 5 prospect overall. The club put him into a big league Spring Training game at 16. It promoted him for the Double-A playoffs at 17.

And on Wednesday night? The Padres asked Salas to backstop a pitcher more than twice his age -- a five-time All-Star and an inter-continental superstar.

Yu Darvish made his first rehab start as he works his way back from a left groin injury that sidelined him late last month. He did so at High-A Fort Wayne, with Salas behind the plate.

Darvish allowed six runs over 3 1/3 innings, though he felt fine according to reports. He didn't exactly have the cleanest game played behind him, either, given the makeup of his High-A-level defense.

Nonetheless, the Padres viewed it as a valuable experience for Salas, who worked minimally with the team's veterans during big league Spring Training. (He mostly caught fellow Minor Leaguers, noting at the time, "If the org thinks we're the guys who are going to work together for a long time, it's really important that we establish that [relationship] early, and I think we did.")

Salas' second professional season is off to a slow start at the plate. His 1-for-3 night while catching Darvish brought his average to .199, though he might be heating up. Salas is 6-for-15 with a pair of walks across his past four games. A team source cited Salas' smaller movements at the plate and his improved timing as signs of a turnaround.

Behind the plate, the Padres remain pleased with Salas' progress. They say he's been solid framing-wise, and he has graded out well over the past couple of months. He's also throwing out runners at a 26 percent clip, well above the MiLB average.

Naturally, Salas has strides to make in his development. He¡¯s an 18-year-old playing the sport¡¯s most demanding position. But the Padres like the progress he¡¯s made recently.

Here¡¯s a quick look around the rest of the farm:

Triple-A El Paso: Nate Mondou was named the Minor League Player of the Week on June 13 after going 9-for-20 with six extra-base hits. Meantime, Graham Pauley (the Padres' No. 6 prospect), has struggled for much of the season, whether in the big leagues or Triple-A. His batting average with El Paso dipped to .212, and he was hitting .180 in June entering Thursday.

Double-A San Antonio: Left-hander Robby Snelling (No. 2) has turned in two consecutive quality starts -- including six innings of one-run ball on Saturday. Offensively, catcher Brandon Valenzuela (No. 11) has begun to heat up in June. He¡¯s hitting .340 with four home runs this month.

High-A Fort Wayne: Playing alongside Salas, Homer Bush Jr. (No. 8) needed just 60 games to reach the mark of 30 steals. He is reaching base at a .365 clip.

Single-A Lake Elsinore: The Storm clinched the first-half division title in the California League this week. Right-hander Isaiah Lowe (No. 19) has starred, posting a 2.86 ERA, including a 0.96 mark across his past three outings, all quality starts.