BALTIMORE, AUG. 5 -- Maybe Ben McDonald really can do no wrong, as the first-inning home run he allowed to George Brett tonight was washed away soon after by the storm that rained out the Baltimore Orioles' game against the Kansas City Royals. The Orioles just wish they had been as fortunate in the day's other developments.

Before McDonald took the mound in his attempt to become the first Baltimore pitcher to win his first four major league starts, the team's recent rash of injuries accelerated toward debilitating levels -- so quickly that a bewildered shake of the head was the expression in vogue in the Orioles' clubhouse this afternoon.

A disheartening pregame procession saw the Orioles place second baseman Bill Ripken on the 15-day disabled list, learn that his designated minor league replacement had been injured 10 minutes before he was to be recalled, then reshuffle the pitching rotation to accommodate Dave Johnson's still-aching back. Manager Frank Robinson was left to muse about using a mostly stationary, 230-pound first baseman nicknamed "Moose" as an emergency third baseman, while trainer Richie Bancells resorted to gallows humor.

As the ranks of the walking wounded grew, Bancells beckoned to a group of reporters nearby in the clubhouse and said: "Stay close to me and watch the trainer commit suicide."

Ripken was diagnosed today as having a stress fracture in his right foot that will keep him sidelined for at least two weeks. He had 14 hits in his last 28 at-bats and had been hitting .297 since May 1 to elevate his season's average from .191 to .280, and he had a 52-game errorless string afield broken Saturday night.

"He'd been playing the best he ever has since I've been here," Robinson said, and Ripken couldn't disagree.

Ripken -- who was replaced on the roster by Jeff McKnight and in the starting lineup by Rene Gonzales -- wasn't certain as to when the injury occurred, but he guessed it came as he lunged awkwardly back toward second base Thursday night after teammate Brady Anderson popped up a bunt attempt. Ripken felt pain in his ankle when he awoke Friday morning, he said, but he simply had extra tape applied and played on it until midway through Saturday's game.

That's when the pain became unbearable and he informed Bancells he couldn't continue after walking off the field in the seventh inning. X-rays late Saturday showed only a touch of arthritis, but a bone scan performed this morning by Hank Dudley revealed a small fracture.

Ripken won't make the team's upcoming nine-day western road trip, and he was told to stay off the foot as much as possible for the next two weeks. He's scheduled to be fit for a removable splint in the morning.

The Orioles' first choice to replace Ripken was third baseman Leo Gomez, who has 21 home runs and 77 RBI for Class AAA Rochester. But when personnel director Doug Melvin telephoned Rochester to have Gomez removed from the Red Wings' game this afternoon, he learned that the prized prospect had just injured his shoulder in a collision at third base and will be out for a week to 10 days.

So Baltimore opted instead for McKnight, a versatile utility man signed as a minor league free agent from the Mets organization during the offseason. He had three hits in 12 at-bats with New York last season, and was hitting .277 in 90 games with Rochester; the 27-year-old also played every position but pitcher at Class AAA Tidewater in 1989.

Meanwhile, Johnson threw for 12 minutes off a mound today and experienced some soreness in his back and legs. He was removed from his start Thursday after 5 2/3 innings, and a series of tests Saturday revealed a strained lower back.

The Orioles' winningest pitcher at 11-6, he was scheduled to pitch Tuesday in Oakland. John Mitchell will start in his place, with McDonald to follow on Wednesday and perhaps Johnson on Thursday, Robinson said.

Ripken and Johnson were added to a rapidly expanding list of injuries that already included pitcher Bob Milacki (on the disabled list with a sore shoulder), first baseman Randy Milligan (sore back) and third baseman Craig Worthington, who said his slight hamstring pull should allow him to return to full-time duties Tuesday.

Tonight's game lasted only 15 minutes before being ended by a heavy downpour and lightning.

No makeup date has been determined; the two clubs were not scheduled to meet again this year. Still, the Orioles (53-54) picked up a half-game on first-place Boston in the AL East.