Giant outfielder Jack Clark: can he catch up to his potential?

The subject was rightfielder and power hitter Jack Clark of the San Francisco Giants and the man doing the talking was batting coach Jim Lefebvre, a former National League Rookie of the Year (1965) with the Los Angeles Dodgers.

''There goes a man with incredible talent whose future is still ahead of him, '' said Lefebvre, pointing in the direction of Clark, who was doing wind sprints in the outfield. ''I can't tell exactly when it's going to happen, but someday Jack is going to realize his full potential and the Giants will suddenly have themselves a superstar.''

It seemed like an odd thing for Lefebvre to say about a player who, at 26, is an established hitter with five years in the big leagues and two All-Star games under his belt. In fact, on a team that has known the likes of Willie Mays, Orlando Cepeda, Willie McCovey and Bobby Bonds, Clark's 26-game consecutive hitting streak in 1978 is the longest ever by a Giant.

Asked why his remarks about Clark seemed tied so much to the future, Lefebvre replied:

''Like a lot of exceptional kids, Jack got rushed so fast through the minors that he never really had a chance to learn his trade at that level. It isn't an unusual situation today because every club in baseball does it.

''They find a kid who looks as though he can learn and contribute while playing every day or nearly every day in the big leagues and they can't wait to get him on their major league roster.

''Well, what Clark has done so far is only the beginning. At some point in his career I'm sure you're going to hear people calling Jack the best hitter in the National League. And they won't just be talking about his power, they'll also be talking about his ability to hit for average.''

Clark, who is 6 ft. 3 in. tall and weighs 205 pounds, was originally a pitcher when San Francisco scouts discovered him. His high school record included 99 strikeouts in 95 innings, plus a 1.25 earned-run average. But once the Giants saw Jack hit, they turned him into an outfielder on the standard theory that any guy who plays every day is more valuable than a pitcher, who, at the most, might get to start twice every eight days.

Lefebvre says one of the reasons the Giants decided to move Clark up so fast was because of his natural aggressiveness at the plate.

''Pitchers try to intimidate hitters by coming inside on them and moving them off the plate,'' Jim explained. ''It's part of baseball, and if the hitter surrenders enough ground, then the pitcher has the outside corner all to himself.

''But the good hitters, like Jack, don't react to those kind of tactics,'' he continued. ''They figure the strike zone belongs to them and so they take it. And that's what makes them so tough.''

Clark's strike zone is anything he thinks he can reach, which makes it tough on any pitcher who might decide to waste a pitch just off the plate. This trait doesn't mean that Jack is a bad-ball hitter, only that if he thinks he can drive the ball safely, he's going to reach out and try to make contact.

''Pitchers don't pitch the same way all the time, at least the good ones don't, so the hitter has to be able to adjust if he's going to make it up here, '' Lefebvre said.

''Clark has always read pitchers very well. The way he constantly shifts his hands and feet in the batter's box is probably too subtle for any fan to pick up , but as a batting coach I watch for things like that all the time.''

The bottom line on Clark, of course, is that he does the job as a hitter day after day, not just once or twice a week.

On a San Francisco team that hasn't finished higher than fourth in the National League West since 1978, Jack is the best drawing card the Giants have. He hits for both power and average and also handles everything well that comes to him in the outfield.

While good defense from a slugging outfielder isn't that unusual, there are enough good National League hitters around who don't have much of a glove to make Jack stand out.