The Mets will hire Tony DeFrancesco to manage their Triple-A Las Vegas affiliate, an industry source said on Friday.

The move marks the beginning of “major changes” planned by general manager Sandy Alderson, who expressed disappointment in the preparedness of the players who were promoted to the Mets during the season.

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DeFrancesco, 54, spent seven years with the Astros, including the last three managing the team’s Triple-A affiliate in Fresno, California, but the Seton Hall graduate was not retained by Houston.

He replaces Pedro Lopez, who managed Las Vegas for one season. Lopez will be reassisgned within the Mets’ organization.

“Just as we didn’t have a good season at the major- league level, we didn’t have a particularly good season at the minor-league level, either, and that needs to be reviewed,” Alderson said earlier this week.

The Mets already have dismissed Triple-A hitting coach Jack Voigt. It’s unclear whether Las Vegas pitching coach Frank Viola will remain in that role.