Washington @ Colorado preview

Last Meeting ( Jul 22, 2014 ) Washington 7, Colorado 4

The first-place Washington Nationals try for a three-game sweep over the Colorado Rockies on Wednesday afternoon, but will almost certainly do so without Ryan Zimmerman. The third baseman suffered a right hamstring strain during Washington's 7-4 victory Tuesday and could be headed for the disabled list. That is bad news for the Nationals, who are 33-19 and average 4.9 runs with Zimmerman in the starting lineup this season, but 22-24 and 3.5 runs per game without him.

Washington has won four straight contests and leads Atlanta by two games in the National League East as it continues a nine-game road trip. Colorado has lost seven straight and is 6-25 in its last 31 games after blowing a lead for the fourth time in five games since the All-Star break. Jorge De La Rosa hasn't lost in five starts (4-0) while winning three straight outings at home and opposes Stephen Strasburg, who hasn't won in three turns despite striking out nine in each start.

TV: 3:10 p.m. ET, MASN (Washington)

PITCHING MATCHUP: Washington RH Stephen Strasburg (7-7, 3.55 ERA) vs. Rockies LH Jorge De La Rosa (10-6, 4.39)

Strasburg yielded four runs and seven hits in seven innings of a 4-2 loss to Milwaukee on July 18 and has only one victory in his last seven turns (1-3) - a 7-1 win over Colorado on July 1. “I’d say the fastball command has been pretty good for the most part,” the 26-year-old California native told the Washington Post. “Maybe I’m throwing too many strikes. Maybe I need to be more effectively wild.” Strasburg yielded three runs and struck out eight in six innings of a 4-2 loss to Colorado on June 25, 2012 - his only start at Coors Field, but gained extensive experience pitching at altitude collegiately while with San Diego State in the Mountain West Conference.

De La Rosa received a no-decision in a 4-2 loss at Pittsburgh on Friday after yielding one run in six innings and leaving with a 2-1 lead. The 33-year-old Mexican is an astonishing 41-14 at Coors Field - 6-2 in 2014 - and told mlb.com earlier this month: "I like it here because I can command my pitches here. When I go on the road the breaking ball breaks too much. I have trouble keeping it in the strike zone. It's not as comfortable as pitching in Coors Field." De La Rosa has yielded four or fewer hits in 11 of his 20 starts this season, tied for most in the majors with Seattle's Chris Young and the Los Angeles Angels' Garrett Richards.

WALK-OFFS

1. Rockies All-Star shortstop Troy Tulowitzki, who has 21 home runs and leads the majors with a .340 average, was placed on the disabled list Tuesday with a left hip flexor strain. It was the first trip to the DL this season for Tulowitzki, who missed 282 games between 2008-13 because of various injuries and days off.

2. Zimmerman was 12-for-26 with two homers and 10 RBIs during an eight-game hitting streak prior to going 0-for-3 on Tuesday.

3. Nationals SS Ian Desmond, who was 5-for-5 on Monday, recorded hits in his first two at-bats Tuesday and extended his streak of reaching base safely to eight plate appearances after getting hit by a pitch before striking out.

PREDICTION: Rockies 3, Nationals 2