The Fresno Grizzlies have signed a two-year contract to become the Houston Astros’ top minor league affiliate, ending a 17-year partnership with the San Francisco Giants that produced two World Series championships.

The move, prompted after the Giants decided to tap the Sacramento Rivercats as their Triple-A affiliate, was announced during a Thursday afternoon press conference at Chukchansi Park.

Grizzlies executives touted the partnership with Houston and said the switch would help field a more competitive team as top prospects the likes of shortstop Carlos Correa and pitcher Mark Appel move their way up the farm system.

“We’re very excited about this opportunity because the Astros have top minor league system and a top farm club,” Derek Franks, Grizzlies vice president of business operations, said as Parker the Bear, the team mascot stood in the background wearing a Grizzlies jersey with an Astros arm patch.

“We couldn’t be any happier with the outcome. We’re thrilled for the next chapter of Fresno Grizzlies baseball.”

The Astros, boasting a farm system that has been rated as baseball’s best by Sports Illustrated and ESPN.com, compete in the American League West Division. A slew of losing seasons has helped the team acquire high draft picks in recent years. Correa and Appel, a former Stanford standout, both were drafted first overall in the 2012 and 2013 MLB Draft, respectively.

The Grizzlies have had talent circulate through their ranks en route to making the Giants roster. Buster Posey, Tim Lincecum and Madison Bumgarner all made stops in Fresno before making the jump to the majors — though many of those were but brief stints.

The Grizzlies’ 17-year partnership­with the Giants featured­World Series teams in 2010 and 2012, but that success came with a tradeoff. The Grizzlies, under the Giants, have only made the Pacific Coast League playoffs once — in 1998.

The ability for fans to watch a more competitive team with young, top talent was arguably the biggest selling point Franks and team president Chris Cummings spotlighted in the new partnership with Houston.

“It’s a next chapter for us that we’re excited about,” Franks said. “One of the things I’ve heard over the years is as much as everyone loves the Giants, they’d love to see a first-place team and a playoff team come to Fresno.”

“Winning seems to cure all,” Franks added. “We think the likelihood of having a winning ball club here … rose dramatically today.”

The Grizzlies brass said it does not plan to change mascots or discard the Giants memorabilia that adorns the stadium — the ballpark has banners of Posey and Bumgarner and “unofficially retired” jersey numbers of former Grizzlies greats — though the team sold its home uniforms and plans to introduce new designs.

Astros team president Reid Ryan, son of Hall of Fame pitcher Nolan Ryan, and other top executives are expected to make a trip to Fresno in October. Cummings said it was his close relationship with Ryan — the two have known each other for 10 years — that helped solidify a deal between the teams during a “mad scramble” transition period.

Six Triple-A teams’ player development contracts with their parent teams expired after the 2014 season.

The Grizzlies’ 2014 season featured heavy speculation the Giants would opt out of renewing their contract with Fresno, which faces revenue struggles and an ownership actively trying to sell the team.

San Francisco made it official this week, when it relocated its Triple-A affiliate to nearby Sacramento, formerly part of the Oakland A’s farm system.

Franks said the Giants were in “constant communication” with Fresno, but ultimately, proximity was the “tipping point” in San Francisco’s decision to sever ties with the Grizzlies.

The discussion period for teams seeking re-affiliation started Tuesday.

“We were committed to getting the Giants back,” Franks] said. “As it got closer, you look at what the scenarios might be, but we really didn’t know until Tuesday who actually was available.”

“We were fortunate enough to talk with every one of the five teams that were available,” Cummings said. “As soon as we start talking with Reed, it all fell together quickly.”

The two-year player development contract between the Grizzlies and Astros is the minor league minimum. “The goal is to go beyond that,” Franks said.

The two­teams said there are similarities between Chukchansi Park and Minute Maid Park. Both are dubbed “pitcher-friendly” ballparks.

“We wanted to have our place that was really a fair park and was a good indicator of what these guys were going to be doing when they come up,” Ryan said, according to the Astros’ official team website.

“We have so much pitching in the system right now, and we felt like having a stadium that was more like Fresno, where the weather was a little more consistent and it wasn’t cold at the start of the season and it wasn’t at altitude. That was a better fit for us.”