Dodgers come off the break with a lot of tough work ahead of them

In the days leading up to the All-Star break, Dodgers closer Kenley Jansen was already looking to the weeks ahead.

“We’re going to have a tough month,” Jansen said. “We have to compete now and show our best.”

The Dodgers resume play Friday at Busch Stadium, where their 2013 season was ended by the St. Louis Cardinals in the National League Championship Series.

The series against the Cardinals will mark the start of a span in which 26 of 29 games will be against teams with winning records. The last 20 games of that stretch will be played on consecutive days.

The Dodgers have the best record in the NL, but they’re about to find out whether that is an accurate measure of their ability or a mirage created by a soft schedule.

The Dodgers are 15-20 against teams with winning records. They were also 1-2 against the Cleveland Indians, who are .500. Against everyone else, they are 38-21.

The upcoming nine-game trip will be particularly tough, as it includes stops in Pittsburgh and San Francisco.

Manager Don Mattingly is particularly mindful of the three-game series against the Giants, who trail the Dodgers by only one game in the NL West.

Dan Haren will start against the Cardinals on Friday because Mattingly wanted to ensure his three best pitchers — Clayton Kershaw, Zack Greinke and Hyun-Jin Ryu — will face the Giants in the series at AT&T Park on July 25-27.

Keys to the second half

Colorado Rockies shortstop Troy Tulowitzki says the Dodgers are in first place because of their pitching. “They have it from top to bottom,” he said.

Dodgers starting pitchers have a combined earned-run average of 3.08, the best in baseball.

There might not be another team that can match the top three of Kershaw (11-2 record, 1.78 earned-run average), Greinke (11-5, 2.73) and Ryu (10-5, 3.44). Veterans Josh Beckett (6-5, 2.26) and Haren (8-6, 4.23) have performed better than expected. Lifelong starter Paul Maholm, primarily a reliever this season, offers the team some depth. Maholm pitched six shutout innings in a 1-0 victory over the San Diego Padres last week.

The rotation is the main reason why Mattingly thinks his team will be able to withstand the upcoming month.

Already, this group has pitched their way into the history books. For 39 consecutive games, the Dodgers starting pitcher walked two or fewer batters, the longest such streak since at least 1900, according to Elias.

Moves to make

With Beckett temporarily sidelined and Haren looking shaky in recent starts, the Dodgers are in the market for pitching. However, based on General Manager Ned Colletti’s comments, it doesn’t sound as if the Dodgers will be bidding for frontline starters such as David Price or Cole Hamels.

The bullpen could also use an upgrade. Jansen, who has 27 saves, and left-hander J.P. Howell, who has a 1.32 ERA, are two of the best relievers in baseball, but Chris Perez (4.54 ERA) and Brian Wilson (5.64 ERA) have been inconsistent.

As for their high-priced outfielders, the Dodgers would probably like to unload one of them, especially with top prospect Joc Pederson waiting in triple A. However, they might not be able to find any takers for Matt Kemp, Andre Ethier and Carl Crawford. Kemp will still be owed $107 million after this season, Ethier $56 million and Crawford $62.25 million.

Kemp would probably be most attractive to other teams, but the Dodgers might not want to part with him. If they do, they would be left with three left-handed-hitting outfielders in Ethier, Crawford and Pederson, to go with the right-handed-hitting Yasiel Puig. Crawford’s frequent visits to the disabled list is a huge red flag to other teams, as is Ethier’s sharp decline in offensive production.

Ethier has four home runs, only one more than utility man Justin Turner, who has 111 fewer plate appearances.

Best-case scenario

Hanley Ramirez is in the final year of his contract and, as he showed last season, he is one of the best hitters in the game when he’s determined. Perhaps the most surprising aspect of the Dodgers’ recent surge is that it’s happened without Ramirez performing at an All-Star level. Dee Gordon reaching base consistently has helped.

“He’s added a speed dynamic, where we can get a run without getting a hit,” Adrian Gonzalez said. “He can walk, steal second, we get him over and get him in.”

If Gordon maintains his production and Ramirez turns back into the hitter he was last season, the offense could be as dominant as the rotation.

The Dodgers would also welcome a return to form by Puig. In the 52 games Puig played through June 1, he batted .347 with 11 home runs and 40 runs batted in. In the 38 games he has played since, he hit .257 with one home run and 12 RBIs.

Worst-case scenario

The Dodgers have five outfielders competing for playing time. Earlier in the season, a similar situation resulted in some grumbling from the players.

Defense could also be a concern. The Dodgers were one of the worst defensive teams in baseball in April, which was reflected in their record. A relapse is entirely possible considering they are weak at two important positions: shortstop and center field.

For better or worse, Ramirez is the team’s shortstop and that won’t change. The best the Dodgers can do to minimize his defensive footprint it to replace him late in games they are leading.

The situation in center field is also unlikely to change. There’s no room on the roster for Pederson. With Kemp’s move to left, the Dodgers have used Ethier and Scott Van Slyke in center, but neither possesses the athleticism of a prototypical center fielder, which has presented problems when the Dodgers have played in spacious ballparks such as Coors Field in Colorado or Petco Park in San Diego.

What’s realistic

The Dodgers have significantly more talent than any other team in the NL West, which offers them a greater margin for error than their rivals. As strong as the Giants have looked at times, their recent slide demonstrated they always will be an injury or two away from a major slump. The Dodgers should win the division, perhaps even by a double-digit margin as they did last season.

dylan.hernandez@latimes.com

Twitter: @dylanohernandez