Mixed in with the regrets about a disappointing ending to the Oakland Athletics' season came at least one promise.

"I'm just sorry the world didn't see the Oakland A's at their best," said A's pitcher Dave Stewart after the Cincinnati Reds completed their four-game sweep of the 1990 World Series."I'm going to go on the record right now," Stewart said. "We'll be back next year."

After three consecutive pennants, nothing short of a World Series victory will suffice for the team that saw any claim of a dynasty shoveled away for another year.

Whether Stewart keeps his promise will depend on several people. Bob Welch, Willie McGee, Scott Sanderson, Ron Hassey and Jamie Quirk are eligible for free agency, and Jose Canseco may be eligible for back surgery.

Center fielder Dave Henderson could find himself a new-look free agent should baseball arbitrator George Nicolau rule in favor of the player's union's proposal regarding the collusion decision against the owners following the 1987 season.

The A's are left with a talented puzzle that must be fitted back together for 1991, but it figures to be an expensive task for Oakland general manager Sandy Alderson.

Bob Welch, who never before won more than 17 games in a season, won 27 this year, and tops the A's list of free agents. Welch, who negotiates his own contract, figures to come up against an Alderson who would love to have him back, but may not be able to afford him.

The A's already have two $3 million pitchers: Stewart and reliever Dennis Eckersley. Add to that Canseco's five-year, $23.5 million package the A's must fund, and there's not a lot of room for big bidding from the Oakland front office.

Canseco's back will be the biggest health concern for the A's. After hitting 34 home runs over his first 85 games, that injury and a finger injury limited him to three homers and 19 RBIs the rest of the season. By the end of the World Series, he was being booed.

That aside, it's the free agents that will shape any Oakland run for a fourth consecutive American League pennant.

Although the team's negotiations with Welch will take the highest priority, McGee and Henderson offer the A's a choice that will determine the offensive personality of the ballclub.

McGee, the 1990 National League batting champion, would give the A's a fleet-footed No. 2 hitter to bat behind Rickey Henderson. Dave Henderson, who hits less for average but with more power, may be the best clutch hitter the A's have. He is also a big presence in the Oakland locker room.

McGee's price - which figures to be around the $3 million range - could force the A's to go with Dave Henderson. Alderson would not mind taking the draft choice as compensation if McGee is signed by another team, the same way he did with Dave Parker, a move that netted him the coveted Todd Van Poppel in last June's draft.

Mark McGwire, who hit 39 home runs and drove in 108 runs this season, could give Oakland another signing problem. His contract is up, and, although he is not eligible for free agency, he will be expecting some big dollars.

And what about Mike Moore? Which Moore will show up in 1991? The guy who won 19 games in 1989 or the 13-15 pitcher in 1990?

So the A's, a team that won 103 games and swept its way into the World Series, has plenty to come to terms with, not the least of which is the distasteful way this season came to an end.

"The whole season my goal was to repeat (as World Series champions)," said Oakland's Carney Lansford. "We had a chance to do it, but we just didn't get that final piece again."