The other day, the San Francisco Giants were so anxious about the lagging pace of Candlestick Park's conversion to natural turf they were talking about switching their season-opening series with the Padres to San Diego. That's nothing -- the Padres (and Giants) are seriously negotiating to play a 1980 season-opening series in Japan!

Yes, the game would count in the National League standings -- and reduce the San Diego Stadium home schedule. But Commissioner Bowie Kuhn evidently is still all for the move as a step toward the supposed nirvana of an eventual global World Series.

Displaced teams? Try the New England Tea Men of the North American Soccer League. A Massachusetts judge has booted them out of Schaefer Stadium in Foxboro and the NASL club (pending appeal) is looking hard to see where they go from there for home field. The Tea Men were losers in court in a struggle with the New England Harness Raceway, adjacent to the stadium, over conflicting dates: starting April 28, nine Saturday nights and seven Wednesday nights.

So Arnold Palmer turns 50 in September So. PGA Tour Commissioner Deane Beman announces that a study is under way into the feasibility of a seniors' tour for name golfers 50 and over beginning in 1980...So Al McGuire, the former Marquette coach and now (to these ears) the most delightful of all basketball commentators, already is hanging it up on his $75,000-a-year corporate executive job with Medalist Industries Inc. So, has the coaching bug grabbed you back, Al? Knicks? Nuggets? USC? UCLA?Says Al, mysteriously, "Hey, it is simply time to move on with my life." And Milwaukee sources indicate coaching is not on the front burner. But --... Incidentally, Oral Roberts U., one of Georgetown's five conquerors the past hoop season, is looking for a new coach. "Personal reasons," said Lake Kelly in quitting, "not under pressure."

Slap ! Some shot former Detroit Red Wing prexy John Ziegler laid on the Wings yesterday because of derogatory statements by G.M. Ted Lindsay about the NHL Players Association: fine of $5,000.

Louder noises coming up at Navy April 6-8. Comic-strip Doonesbury's "Uncle Duke" character would love it: the first shoulder-to-shoulder (no way they'll call it head-to-head) National Intercollegiate Rifle Championships. It will pave the way for the first NCAA nationals in the sport next year. National Rifle Association, sure, is lending its expertise...