SAN DIEGO – No matter what they try, the San Diego Padres just keep losing.

The NL West-leading Padres lost their 10th straight game Sunday as Melvin Mora hit a go-ahead single that sent the Colorado Rockies to a 4-2 win.

“We have a sense of urgency right now,” Padres pitcher Clayton Richard said. “We have a special opportunity and we are going to do every thing in our control to take advantage of it.”

Mora’s tiebreaking hit in the seventh inning gave Colorado its 10th win in 14 games. The Rockies pulled within 4 1/2 games of the slumping Padres.

The Padres, who have led the division virtually the entire season, have seen their season-high 6 1/2 game lead on Aug. 25 nearly evaporate. San Diego began the day with a two-game edge over San Francisco, which played a night game at Dodger Stadium.

San Diego has not won since a 9-3 victory over last-place Arizona at home on Aug. 25. Since then, the Padres have been outscored 55-23 and have watched their top-rated pitching staff and defense falter, along with an offense devoid of key hits.

“We’re in games but we’re not generating the big hit, not generating the offense to get us over the top,” San Diego manager Bud Black said. “We have to turn this around. It’s in us because I’ve seen it. But we haven’t done it the last 10 games.”

It looked like Miguel Tejada’s towering two-run homer in the sixth inning that tied the game at 2-all might give the Padres momentum. But Mora’s hit sent them to another defeat.

The losing streak is starting to take on near historical dimensions. The streak is San Diego’s longest since a franchise record 13-game skid in May 1994. Plus, only two teams in major league history have made the postseason in a year that included a losing streak of at least 10 games.

“I don’t think we can be too hard on ourselves,” Tejada said. “We just have to keep playing hard and we have to be positive. We’re still in first place.”

The Rockies completed the three-game sweep and have won 11 of 15 games this season against the Padres, including seven of nine at Petco Park. This was Colorado’s first road sweep since Aug. 18-20, 2009, at Washington.

“I think it goes without saying, this was a tremendous series for us,” Colorado manager Jim Tracy said. “It has brightened the picture considerably over the course of the last three days.”

The Rockies, who have not been this close to first place since July 23, also moved within 5 1/2 games of Philadelphia in the wild-card race.

“We have a really good opportunity to win the division,” said Colorado’s Carlos Gonzalez. “We just have to keep playing good baseball.”

Tejada’s fifth homer hit off the front of the third deck of the Western Metal Supply Company building down the left-field line and came right after Adrian Gonzalez doubled with one out in the sixth.

But Mora came right back and delivered his go-ahead single in the seventh off reliever Mike Adams.

Gonzalez got the inning going with a one-out single off Tim Stauffer (3-3), and walk to Troy Tulowitzki brought on Adams. After a double steal, the Padres played the infield in and Mora’s ground ball got by second baseman David Eckstein into right field.

“Melvin Mora has a history of being a guy that loves to take a big at-bat in a game,” Tracy said.

Tulowitzki hit his 14th homer leading off the fourth against Richard. Tulowitzki also drove in a run in the fifth when third basemen Chase Headley failed to cleanly field a groundball that could have potentially led to an inning-ending, double play.

Jorge De La Rosa (6-4) allowed two runs on six hits over six innings. Huston Street pitched the ninth for his 15th save in 19 chances.

Gonzalez went 3 for 5, raising his NL-leading average to .337 and extend his hitting streak to 13 games. Gonzalez is hitting .529 (27 for 51) during the streak.

Richard gave up two runs — one earned — on nine hits in six innings.

Notes: The two clubs that reached the postseason with losing streaks of at least 10 games were the 1951 New York Giants and the 1982 Atlanta Braves. … Tejada played in his 2,000th career game, which includes a streak of 1,152 consecutive games that was snapped in 2007 when he broke his left hand. … Tejada stole second base on his first attempt of the season in the second inning. … Colorado swept the Padres for the first time on the road since September 2007. … San Diego RHP Chris Young threw 3 1-3 hitless innings in a rehab start for Triple-A Portland against Las Vegas. Young, who has been on the disabled list with a strained right shoulder since April 12, was making his second rehab start.