As reigning World Series champions, the Philadelphia Phillies had every reason to feel smug when the split-season plan was announced.

After all, they had won the World Series last season, finished first in the first half of their division race and clinched a playoff spot. So, why get all excited about the beginning of the second half?

Well, the champions played like tailenders in their first nine games, winning only twice. When they returned here to start a six-game home stand, Manager Dallas Green slammed the clubhouse door and held a 30-minute meeting.

Since then, the team has beaten the Houston Astros, 5-4, Friday night and 8-4 today with its biggest home run output of the season.

Substitute catcher Keith Moreland hit two balls over the left field fence and Manny Trillo hit one homer. And, of course, Mike Schmidt had to get into the act, hitting his 19th, into the lower deck with Gary Matthews on base in the fifth inning.

Although it was the first time this season that the Phillies had hit four homers in one game, Green wasn't about to credit his meeting for the resurgence.

"I don't think the meeting did it," he said. "It wasn't that kind of meeting. It was cool, calm and collected. But the next one won't be. They've been told that."

After a long pause for effect, Green shifted gears quickly and praised his team.

"We've got five guys swinging pretty good right now," he said. "It looks like Gary Matthews is coming out of it (two singles and a sacrifice fly in four trips) and Manny Trillo, too."

Trillo, who has been struggling since the season resumed, hit a single, double and home run in his three times at bat before giving way to John Vukovich in the seventh.

"Two games don't make a year," Green continued. "But I've seen some good things lately and that's encouraging."

The most encouraging performance today was that of Moreland, who is making inroads into Bob Boone's domicile behind home plate.

The 27-year-old catcher has started the last three games and, although he won't play Sunday night because Steve Carlton is starting, he's made a fine impression with his handling of pitchers and his hitting.

"It's nothing new to us that Keith is hitting the ball this way," Schmidt said. "He's hit in every league he's ever been in."

In addition to earning all-America honors as a third baseman at the University of Texas, Moreland was a starting defensive back for Darrell Royal's Longhorns as a sophomore and was an excellent basketball player in high school.

Moreland was brought up from Oklahoma City in the waning weeks of the 1979 season and hit .375 on 18 hits in 48 tries. Last season, backing up Boone, he batted .314 in 159 at-bats.

Now, with Boone, 33, limping along with a .227 average, Moreland is being given every opportunity to earn a regular job.

"I'm not in a position to say what's going on," Moreland said. "When you see your name on the (lineup) board, you just go out and play as well as you can.

"Bobby Boone is still the best in the business," Moreland continued. "I still think he's going to play and do the job for us like he's done the last seven years."

Despite his limited duty, Moreland has five home runs, which puts him second on the team behind Schmidt. And winning pitcher Dick Ruthven praised Moreland's choice of pitches today.

"Keith has improved a lot since he's started playing more," said Ruthven, who pitched six strong innings before giving up three runs in the seventh and yielding to Sparky Lyle. "Everyone knows he's a tremendous talent."

Moreland's first homer was important because it put the Phillies in front, 1-0, in the second inning. They got two more in the third on successive singles by Ruthven, Pete Rose and Bake McBride, plus Mathews' sacrifice fly.

Moreland walked and scored on Trillo's homer in the fourth to make it 5-0 and dispose of Houston starter Joe Niekro (7-7).

The Phillies' final three runs came in the fifth when Matthews walked, Schmidt homered into the left field stands and Moreland matched it.

Houston's only big inning was the seventh. Ruthven said later that it felt like he "was throwing underwater." Doubles by Cesar Cedeno and pinch hitter Denny Walling, sandwiched around a walk and followed by Tony Scott's single, made it 8-4, but once Lyle entered, the Astros were finished.