Bryce Harper plans to return Monday in Philadelphia. (Brad Mills/USA Today Sports)

NEW YORK — Barring a last-minute setback, the Washington Nationals will activate Bryce Harper ahead of Monday’s game in Philadelphia, according to people familiar with the situation. Harper has been out since Aug. 12 with a bone bruise in his left knee and a left calf strain suffered when he slipped on a wet base.

Initially, the injury looked gruesome enough that Harper’s season seemed certain to be over. Soon after, he and the Nationals began a rehabilitation race against the late-summer clock. If Harper is, indeed, activated Monday, they will have won that race, giving Harper a week’s worth of at-bats and games before October.

Dusty Baker refused Sunday to commit to Harper being activated, as is the Nationals’ way.

“We’re still trying to make up our minds,” said Baker, who speculated that reporters would spend all night trying to find out. “We’ll let you know tomorrow.”

Baker’s unwillingness to commit is in keeping with the Nationals’ general approach to all injury-related matters. If they do not say for sure that Harper will return, they cannot be questioned if something changes and he doesn’t. So their official stance, as communicated by their unofficial spokesman Baker, is no stance at all. Maybe Harper will return Monday. Maybe he won’t.

But if all goes to plan — and everything has so far — Harper will be active against the Phillies. Whether he is able to play every day for the rest of the season remains to be seen.

Neither Harper nor the Nationals committed to a timetable for the slugger’s return. Privately, both have targeted the last week of the regular season for the last week or so, hoping the 24-year-old would be able to return in time to get major league at-bats before the playoffs. Everything has gone according to plan, including the two simulated games the Nationals built for him this week and the daily batting practice sessions on the field.

Harper has not played in an actual game since the injury, since he was not ready to go on a rehab assignment before the minor league seasons ended. When Nationals players work their way back from leg injuries, they usually do so by increasing their workload incrementally — three innings, then five innings, then seven, and so on. Harper probably does not have time to progress so slowly, but seven straight days of nine full innings does not seem likely, either.

The Nationals could have sent him to West Palm Beach, Fla., where the Nationals’ instructional league season begins Monday, where he could ease back into low-pressure situations. Instead, he will stay in the big leagues, where he has time to get 15 to 20 at-bats before the end of the regular season — and will get them against major league pitching.

While Harper said Saturday the key for him will be regaining his timing, the key for the Nationals will be his stamina. Baseball games require a unique sort of leg strength. Standing in cleats for three hours at a time while starting and stopping on demand is a difficult thing to duplicate. Harper has not done that since the injury. Fatigued muscles are at risk of injury. The Nationals have been particularly slow and steady when nursing stars back to health this year and seem unlikely to make a stark departure from that policy, despite the time crunch imposed by October.

However much he plays in this last week will be plenty for the Nationals, who can now count on one of the most productive offensive players of this generation to be among them in October.

“It’s going to be great,” said Max Scherzer, whose eyes lit up at the prospect of Harper’s return. “… But when you put him back in the lineup, our lineup is scary. We can score runs with the best of them.”

Baker hit Harper third in the lineup before the injury, setting up a lefty-righty-lefty-righty heart of the order that created late-inning nightmares for opposing managers. Wherever Baker hits him initially, Harper will make the lineup one slugger deeper — and it wasn’t lacking power to begin with. Harper’s return also will shift Jayson Werth back to left field, where he will likely compete for October innings with Howie Kendrick.

With Harper in right, the Nationals will have their intended starting lineup (minus Adam Eaton) for the first time since late May. They will have their full team, remodeled bullpen included, for the first time all season. After a season spent fighting off injuries as much as competition in the standings, the Nationals will be whole again — just in time for October.

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