Span will try to become the second Nationals player to register a 30-game hit streak in Thursday night's series opener against the Miami Marlins.
Span extended the longest hitting streak of the 2013 season with a single in the seventh inning Wednesday but the Nationals (81-71) fell 5-2 to NL East-leading Atlanta. Washington's loss was only its second in 12 games but was a big blow to a club that still faces a 5 1/2-game deficit to Cincinnati in the race for the NL's final wild-card berth.
"We just can't afford to lose," manager Davey Johnson said after the end to a three-game win streak. "We've just to start another win streak. It's that simple."
Span will try to match teammate Ryan Zimmerman's 30-game run from 2009, the longest since the relocation from Montreal following the 2004 season. Vladimir Guerrero had a franchise-record 31-game run for the Expos in 1999.
Dan Uggla was the last major leaguer to have a hit streak of 30 games or longer, a 33-gamer July 5-Aug. 13, 2011, for Atlanta.
Span, batting .371 during his streak, is hitting .341 against Miami (56-96) this season and is 4 for 6 with two doubles all-time against scheduled starter Henderson Alvarez (4-4, 3.97 ERA).
Alvarez is coming off a dominant 3-0 win at the New York Mets on Saturday. The right-hander allowed four hits and walked none over seven innings and is 2-0 with a 2.08 ERA in his two road starts this month.
"It's nice to get the solid pitching performance from Alvarez. He looked great," manager Mike Redmond said.
Alvarez gave up one run in 1 2-3 innings in Washington on Aug. 28 before a rain delay ended his start in a 4-3 defeat. He allowed two runs over 6 2-3 innings July 14 in his only other start against the Nationals this season but did not get a decision in a 5-2 loss.
Stephen Strasburg was originally scheduled to start for Washington in this game but his return from forearm tightness was pushed back until Saturday. The Nationals will instead send out Gio Gonzalez (10-7, 3.40).
Gonzalez had a three-start win streak snapped Saturday with a 5-4 defeat to Philadelphia. He gave up four runs and nine hits over six innings after posting a 0.42 ERA in his previous three starts.
Gonzalez began that impressive stretch with a 9-0 win over Miami on Aug. 29, yielding three hits and three walks while striking out eight in seven innings. The left-hander has pitched 13 scoreless innings against the Marlins, losers in 10 of 13.
Miami earned one of those rare wins Wednesday, 4-3 in 10 innings at Philadelphia, as Ed Lucas hit the tiebreaking solo homer.
A second straight victory looks unlikely as Miami has dropped all six games in Washington this season and six of the past seven overall matchups.
The Nationals will try to secure the franchise's first set of back-to-back winning seasons since Montreal finished 83-79 in both 2002 and 2003.