Big changes are inevitable in a regime change, and the Giants are no exception.

In the first of what could be many such moves, the Giants fired eight of their 20 pro scouts Tuesday, including some who have been with the organization for more than two decades and provided invaluable information during the club’s three World Series title runs.

The most recognizable names are Brian Johnson, of 1997 home run fame, and Steve Balboni, both of whom served as pro scouts for the past 10 seasons and were relied on heavily during the 2010, 2012 and 2014 postseasons.

Johnson lives in Detroit and saw the Tigers a lot in 2012. Giants officials credited the intelligence he provided with helping them sweep Detroit in the World Series.

“We had a good run,” Johnson said by text. “No bitterness at all. I am grateful for my time with the Giants. Ten years. Loved it.”

Others let go include Matt Nerland, who has been with the Giants for 31 years and once served as scouting director; Darren Wittcke and Glenn Tufts, both of whom had more than 20 years in the organization; and Andy Skeels, Bob Mariano and Tim Rock.

President of baseball operations Farhan Zaidi said the dismissals followed a season-long review of how the Giants structured their scouting as well as an assessment of each individual.

Zaidi expects some of the scouts to be replaced, and the Giants already have spoken to candidates who have relationships with Giants officials. Zaidi also said changes in how the Giants scout big-leaguers could be coming.

He suggested the trend toward using more video to assess big-leaguers makes some sense, and the organization might be better served sending more scouts to see players at lower levels.

Either way, Zaidi said, “I don’t see any dramatic changes in coverage. We’re still going to be sending guys out to ballparks at all levels.”

Zaidi did not explain why he picked the eight scouts he let go, but praised their work.

“It’s a good group of people who made contributions to this organization, in some cases over a long time, and have been part of some big moments in Giants history on the field, too. It’s obviously sad in that respect, but obviously we’re really appreciative of their contributions over that time.”

Zaidi plans to complete a similar review of the amateur scouting department, which has not been touched yet, as well as the front office and coaching staff. Changes in all three are expected now that Zaidi has had a season to assess their work, and with a new manager coming on board.

“I think anytime you come into a new situation, you probably have a certain style of doing things and things are inevitably going to change,” he said. “You give people the benefit of the doubt and want to evaluate how things are working. Do you have the right personnel? Do you have the right functions? That’s kind of been an ongoing evaluation process in the organization as well.”

Although the eight scouts were let go now to give them a head start on finding new jobs, Zaidi is not doing so with the coaches yet because, he said, they are still “grinding” every day on the field. But he expects to talk to each member of Bruce Bochy’s staff before the season ends.

Henry Schulman is a San Francisco Chronicle staff writer. Email: hschulman@sfchronicle.com Twitter: @hankschulman