SAN DIEGO -- Joe Musgrove has had five pitching coaches in the past four seasons. He’s had four managers in that time.

He’s going to add another coach and manager temporarily later this month -- at the All-Star Game.

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Musgrove’s improvement from year to year, no matter the circumstances, culminated in his first All-Star selection on Sunday, when he was named as a reserve to the National League squad. Musgrove joined Manny Machado, voted in as the starter at third base, as the Padres’ contingent for the July 19 Midsummer Classic at Dodger Stadium.

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“No harder worker than Joe out there,” Machado said. “It’s well-deserved. This guy goes out there and grinds every single day, puts in 110 percent in everything he does around the clubhouse and being with his teammates, everything he does. To finally see him get one is something special.”

Musgrove learned of the honor when manager Bob Melvin told him just before the Padres’ series finale against the Giants. He was still taking it in when he spoke postgame.

“A lot of things aligned to make it a little more special,” Musgrove said. “I’ve been trying to get this selection for five or six years. … I don’t think I’ve been an all-star at any level since I was like 9 years old.”

Musgrove has blossomed in his two years in San Diego, rising to become the Padres’ de facto ace in a rotation that includes former All-Stars Yu Darvish and Blake Snell, as well as baseball’s former top pitching prospect, rookie MacKenzie Gore.

Musgrove, 29, is 8-2 this season with a 2.09 ERA in 15 starts. The right-hander has career-best marks with a 183 ERA+ and a 0.93 WHIP.

“From the very beginning, from Opening Day to this point, he’s been one of the studs in the National League,” Melvin said. “It’s very deserved. … It’s just another feather in his cap and furthers his career into [being] a big-time pitcher.”

Musgrove provided the Padres’ rotation with stability when it most needed it. He was pitching deep into games from the first week of the season and opened the year with 12 straight quality starts, a franchise record to begin a season. As the season began, the Padres had to be careful with pitch counts after the short Spring Training after the labor lockout. Snell and Mike Clevinger were still working their way back from injury, and Gore was in the Minors.

Musgrove, meanwhile, was a horse -- with blinders on.

That ability to focus on the task at hand and eliminate possible distractions has served Musgrove well. In the past four years, he has played for managers Clint Hurdle, Derek Shelton, Jayce Tingler and Bob Melvin and worked under pitching coaches Ray Searage, Oscar Marin, Larry Rothschild, Ben Fritz and Ruben Niebla. He was also traded from the Pirates to the Padres.

Yet Musgrove has lowered his ERA in four straight seasons while evolving as a pitcher. Once a typical fastball/slider right-hander, Musgrove has become anything but typical. He keeps batters off-balance with six pitch options and has used four of them -- slider, four-seamer, curveball and cutter -- at least 17.1 percent of the time. In each of his two seasons in San Diego, he has thrown the slider more than the four-seamer, something he never did in his first five big league seasons.

“Over the last couple years, I’ve really gotten an understanding of who I am as a pitcher,” Musgrove said. “That stuff is discovered through the years with all those pitching coaches. It’s not 100 percent buying into one person’s theory or their methods; it’s just picking the things that help me and picking the little parts I want to add to my game.

“I feel like I’m a culmination of all these different pitching coaches and players and catchers I’ve worked with over the years.”

What convinced him he could use the slider more than the fastball?

“The hitters not hitting it,” Musgrove said. “It’s as simple as that. I never intended to be a thumber, but they aren’t hitting it well.”

Opponents are batting .134 against his curve, .149 against his slider, .229 against his cutter and .236 against his four-seamer.

Those are All-Star numbers.