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8/13/2013 6:59 P.M. ET

Scutaro a late scratch with stiff back; Arias fills in

WASHINGTON -- About 45 minutes before Tuesday night's scheduled first pitch at Nationals Park, the Giants announced that second baseman Marco Scutaro was scratched from the lineup with a stiff back. Joaquin Arias replaced Scutaro and batted second, as manager Bruce Bochy opted not to alter the batting order for the series opener against the Washington Nationals.

Scutaro, 37, endured back problems in Spring Training and early in the regular season, but had mostly avoided them since. He has started 100 of San Francisco's 118 games -- 97 at second base and three as the designated hitter. A National League All-Star selection this year, Scutaro entered Tuesday batting .304 with two home runs and 23 RBIs.

Arias received his 31st start of the season, and his first at second base. He had started 14 games at third, 10 at shortstop and six at first base.

Neither player entered the game having fared well against Washington starter Gio Gonzalez. Scutaro owned a .105 average (2-for-19) off Gonzalez, compared to Arias' .111 (1-for-9).

Pagan could start rehab stint this week

WASHINGTON -- Center fielder Angel Pagan's recovery from his strained left hamstring has progressed so rapidly that he could begin playing in Minor League injury-rehabilitation games by the end of this week, Giants manager Bruce Bochy said Tuesday.

Dave Groeschner, the Giants' head athletic trainer, presented the encouraging report after checking on Pagan at the organization's training complex in Scottsdale, Ariz., during Monday's off-day.

Bochy even said that Pagan could rejoin the Giants before Sept. 1, which reflects wild optimism. Players must be on the 25-man roster by then to qualify for postseason participation.

Pagan was expected to be sidelined for 10 to 12 weeks when he underwent surgery on June 25, a timetable that threatened to sideline him for the rest of the year. In 46 games before being shelved, San Francisco's leadoff batter hit .262 with three home runs, 24 RBIs and 30 runs scored.

Belt's resurgence, confidence being recognized

WASHINGTON -- Brandon Belt batted third against a left-handed starting pitcher Tuesday for the second time in three games. Until recently, that never would have happened.

Then again, Belt hasn't maintained his current consistency until now.

The left-handed-batting Belt's position in the batting order against Baltimore's Wei-Yin Chen last Saturday and Washington's Gio Gonzalez on Tuesday reflected his rising stature and performance, which was recognized as he won National League Player of the Week honors. Belt hit .440 (11-for-25) last week, with two home runs, five RBIs and eight runs scored.

Any doubts about the club's faith in Belt, as well as his faith in himself, just might be a thing of the past.

"I think the confidence is pretty high all the way around, on my side and the coaches' side right now," Belt said Tuesday.

With a .438 average in August entering Tuesday, Belt also has a shot at the Player of the Month Award.

Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.