"I have to make sure we don't think we can just show up and we're going to win because we got new guys," Mattingly said on Monday. "We've got to play and we know it. I don't feel there's any guarantees and the players know that, too."
The remaining challenge was abundantly clear on Monday night, when the Rockies opened the three-game series with a 10-0 blowout. That made the Dodgers 1-2 since they added Josh Beckett, Adrian Gonzalez and Nick Punto to a list of acquisitions that already included Joe Blanton, Hanley Ramirez and Shane Victorino. After five losses in its last seven games, Los Angeles trails by 2 1/2 in both the National League West and Wild Card races.
The Dodgers will look to turn things around on Tuesday with left-hander Chris Capuano. It will be Capuano's fourth outing against the Rockies this season. While he has allowed three runs in 14 innings over two home starts, Colorado touched him up for seven runs, four earned, in 5 1/3 innings on June 1 at Coors Field.
Capuano, 11-9 with a 3.38 ERA on the season, matched a season high by surrendering six earned runs on Wednesday against the Giants. San Francisco plated three runs in the first and three more in the sixth.
"Tonight was like alpha and the omega," Capuano said afterward. "Innings two through five were great. We were attacking the zone and getting quick outs. The first and last inning, I made some mistakes in the middle of the plate. These guys made me pay tonight."
The Rockies, who have won seven of nine, will counter with Tyler Chatwood. The 22-year-old righty is 3-3 with a 4.98 ERA overall, and 2-2 with a 3.38 mark since joining the starting rotation at the beginning of the month.
But Chatwood also has walked 10 and struck out only 12 in his five starts. On Thursday against the Mets at New York, he labored through 65 pitches in three scoreless innings before exiting, 10 pitches short of manager Jim Tracy's limit.
"That's your job as a starter. You go out there for as long as you can and keep your team in the game," Chatwood said afterward. "Today it just happened to be shorter than normal, but I felt like I kept us in the game for as long as I was able to."
Dodgers: Wall rudely welcomed back to Majors
Mattingly knows Coors Field can be an unforgiving place for an overworked bullpen, so the Dodgers took a preemptive measure by recalling right-hander Josh Wall for Monday's series opener. Righty Shawn Tolleson was sent down to Class A Rancho Cucamonga to clear a roster spot.
Tolleson had pitched on Sunday, his third game in five days. Wall provided a fresh arm, but surrendered three runs in one-third of an inning on Monday, his second career big league appearance.
"It's just protection," Mattingly said of the roster move. "We had to use the bullpen, and coming in here [Coors Field], you know what can happen."
With the arrivals of Victorino and Gonzalez, Juan Rivera's playing time figures to decrease significantly. The veteran has started 39 games at first base and 24 in left field this season, but those spots are now filled by everyday players. Rivera also is 3-for-15 as a pinch-hitter.
Rockies: Dodgers series provides 'terrific challenge'
Tracy, a former Dodgers skipper, isn't playing down the potential impact of the club's trades.
"It is a big deal," he said before Monday's game. "They acquired significant players in the deal. They deepened themselves if it plays out. It makes them very formidable."
With the Rockies building toward the future, Tracy was looking forward to the matchup.
"It's a terrific challenge for our young players to go out there and play against a group like this one," he said. "I think in relation to what I've seen over the last three weeks, our guys will embrace this challenge."
Center fielder Dexter Fowler still is unable to play in the field after rolling his ankle on Wednesday against the Mets in New York. He pinch-hit on Saturday and Sunday, but missed his fifth straight start on Monday.
Capuano is 2-5 with a 4.38 ERA in eight starts since the All-Star break. However, he has a 45-to-11 strikeout-to-walk ratio during that span.
Chatwood hasn't faced the Dodgers this season but started twice against them last year when he was with the Angels. In 12 innings, he allowed five runs on 16 hits.