IT SHOULD HAVE gone down as one of their most impressive victories of the season. Their young No. 2 starter shut down a Red Sox lineup that scored 22 runs against them in a three-game series last June. Their left/right combination in the middle of the order drove in four runs, including Ryan Howard's solo home run in the fourth inning and Jayson Werth's towering two-run shot in the fifth, both off starter John Lackey.

The Phillies began interleague play with an impressive 5-1 victory over Boston last night that ended when David Ortiz lined out to deep centerfield with the bases loaded in the ninth.

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Yet it was impossible to ignore a potential loss after shortstop Jimmy Rollins pulled up lame a third of the way to first base on a single to rightfield in the sixth inning. The diagnosis was sunny given the circumstances - a mild strain of his right calf, the same muscle that caused him to spend 5 weeks on the disabled list - but even Rollins acknowledged afterward that his immediate future was unknown.

Asked whether he had any idea whether a trip to the disabled list was possible, Rollins shook his head. "About as good [of an idea] as yours," he said.

The injury came on the day that Rollins returned to the leadoff spot, and only 4 days after he was activated from the DL list following a lengthy rehab of what had been diagnosed as a midgrade calf strain.

Rollins said afterward the injury did not feel as bad as the one he suffered on April 12 while running sprints in the outfield before the Phillies' home opener against the Nationals.

"Not at all," Rollins said, "which is a good thing. It's not tender to the touch. I'll see how it feels tomorrow."

But at the bare minimum, Rollins appears set to miss the rest of this weekend series against the Red Sox, who took two out of three from the Phillies at Citizens Bank Park last summer. He said there are no immediate plans for an MRI exam, although he could have one on Monday's off day.

Until then, veteran Juan Castro, who replaced Rollins on first base after the injury last night, likely will start at shortstop. Coincidentally, the injury occurred on the same day the Phillies learned backup infielder Wilson Valdez had cleared waivers and accepted an assignment to Triple A Lehigh Valley. Valdez, who played solid defense and had a few big hits while splitting time with Castro at short, was eligible to be claimed by another big-league team, which the Phillies thought was a possibility.

Instead, he will be recalled if Rollins needs a second stint on the DL.

Rollins doesn't sound convinced he'll need one, though.

"An hour later, it feels a lot better than it did when I came out," he said, "so we'll see."

The Phillies wound up winning last night, thanks largely to the efforts of Howard, Werth and lefthander Cole Hamels. Hamels (5-2) was particularly impressive, allowing a solo home run to Victor Martinez with two outs in the first inning before settling in to one of his most productive starts of the season. After Martinez' home run, Hamels allowed only three more baserunners. He finished with 116 pitches, allowing one run on three hits with eight strikeouts in seven innings. His fastball, which has been noticeably stronger than a year ago, reached 95 mph a couple of times, and sat around 92 to 93.

The Phillies gave him all the runs he needed in the fourth inning, as Howard hit his eighth home run of the season and Shane Victorino added an RBI single.

Werth's two-run shot came in the fifth, and Howard added an RBI single in the sixth.

Lefthander J.C. Romero inherited runners on first and second with one out in the ninth inning and retired two of the three batters he faced to record his second save of the season. After he hit Adrian Beltre with a pitch to load the bases, the last at-bat featured a showdown between Romero and the lefty slugger Ortiz, who were teammates in Boston in 2007.

Romero got ahead of Ortiz, 1-2, before giving up a loud, long line drive that died in Victorino's glove at the warning track.

The Phillies improved to 26-15, but couldn't overlook the loss of Rollins.

"It was a big win, but at the same time, we didn't want to lose J-Roll," manager Charlie Manuel said. "We need him in our lineup. We need him playing."

When that will happen again remains to be seen.

Phillers

Lefthander J.A. Happ (forearm strain) threw 30 fastballs in a bullpen session and will continue rehabbing in Clearwater, Fla., starting Tuesday, when the team goes on the road, starting with a trip to visit the New York Mets. Happ still needs at least two more bullpen sessions before he gets into a game, and remains at least several weeks away from returning, but both he and pitching coach Rich Dubee were happy with his progress yesterday . . . Righthander Brad Lidge (elbow) played catch for the first time since Monday, when he received a cortisone shot aimed at clearing out inflammation in his elbow. But there are no immediate plans for him to throw off a mound, and he is unlikely to be ready to return when he is eligible to be activated from the disabled list May 25. *

For more Phillies coverage and opinion, read David Murphy's blog, High Cheese, at http://go.philly.com/highcheese.