Even the off days are difficult ones for the Phillies right now.

Instead of rest and relaxation, the Phillies had to do some roster juggling Thursday as they prepared for the start of Friday's three-game series against the San Diego Padres.

Phillies general manager Ruben Amaro Jr. said the team is "probably going to make some changes over the next few days," but he refused to comment on the Twitter revelation from recently demoted reliever Michael Schwimer that the team has promoted infielder Hector Luna and pitchers Jake Diekman and Raul Valdes from triple-A Lehigh Valley.

"Our job is to try to make the team as good as it can be," Amaro said.

Right now, of course, the Phillies are a last-place team that is four games under .500 for the first time since May 9, 2007, the year the team won its first of five straight National League East titles.

These Phillies have an abundance of issues, but the biggest immediate problem is the bullpen's inflated earned-run average of 5.59, by far the worst in the major leagues. The relief was particularly shoddy during the New York Mets' three-game sweep of the Phillies as eight pitchers combined to allow 12 runs on 13 hits, including three home runs, in 71/3 innings.

"We have the ability there, we just haven't pitched particularly well," Amaro said.

Poor performance is not the only reason the Phillies figure to have two new arms in the bullpen when they play the Padres this weekend.

After lefthander Joe Savery was optioned to triple-A Lehigh Valley, it was obvious that the left-handed Diekman would soon be in Philadelphia. The 25-year-old lefty who was so impressive in spring training has earned the promotion by dominating in his first exposure to the International League.

Diekman is 1-0 with five saves, a 0.59 ERA and 22 strikeouts in 151/3 innings for the Iron Pigs. He has walked only three batters, a sign that his control has improved over a year ago when he walked 44 batters in 65 innings at double-A Reading.

"Very impressive," said a National League scout who recently saw Diekman.

The other two moves the Phillies figure to make official Friday are because of injuries.

The two most serious problems appear to be with reliever Chad Qualls and first baseman/outfielder Laynce Nix.

Manager Charlie Manuel said after Wednesday night's game that Qualls was not available even though he had only thrown three pitches in the previous five days. After the game, he was wearing a brace around his left knee.

If Qualls goes on the disabled list, he will join relievers Michael Stutes and David Herndon, neither of whom is expected to begin throwing for "at least two or three weeks," according to Amaro.

"Obviously not having personnel and the depth hurts," Amaro said. "Add the fact a couple guys haven't performed well and that makes it doubly difficult. Guys have the ability to pitch better."

The addition of Valdes will give the Phillies three lefthanders in the bullpen. Valdes, 34, has a career 3-4 record with one save and a 4.58 ERA in 51 big-league appearances. He was 1-2 with a 3.86 ERA at Lehigh Valley and had struck out 26 batters in 21 innings.

Luna, 32, is likely joining the Phillies because Nix appears headed for the disabled list. Nix aggravated a calf injury after contributing a pinch-hit RBI single Wednesday night against the Mets. Nix could barely make it to first base after his single and Carlos Ruiz entered as a pinch-runner.

"He was very sore," Amaro said.

Ruiz was also out of the lineup Wednesday and did not take batting practice because of a sore wrist.

"We'll see how he feels tomorrow," Amaro said. "I think he's going to be OK."

Amaro said he also believes Ty Wigginton will be fine despite being slowed by a sore side that he iced after Wednesday's game.

Luna, after a strong showing in spring training, was hitting .274 with 10 extra-base hits and 12 RBIs at Lehigh Valley. He hit .324 in his last 10 games and was in the midst of a six-game hitting streak.

Injuries aside, including the two biggest ones to first baseman Ryan Howard and second baseman Chase Utley, Amaro is displeased with the way his team has played through the first five weeks of the season.

"The thing that has disappointed me is that we haven't played good fundamental baseball," Amaro said. "The way we've played is unacceptable for a club like this. It's probably a combination of things. Some guys are trying to do too much and other guys aren't doing enough."

Amaro said he has had conversations with other teams, but trades are difficult to make at a time of year when virtually every team still believes it has a chance to play in the postseason.

"Any trade I would make right now would be moot if the guys we are asking to play do not perform better," Amaro said. "Right now, different parts of the club are not performing well and we're all in this together. Everybody has to do their job better."