PHOENIX (Ticker) -- Four-time Cy Young Award winner Randy Johnson may be known as the "The Big Unit" but he continues to come up very small in Division Series competition.

Jim Edmonds and Scott Rolen hit two-run homers off baseball's best pitcher and the St. Louis Cardinals scored six times in the seventh inning en route to a 12-2 triumph over the Arizona Diamondbacks in the opener of their National League Division Series.

St. Louis jumped on Johnson - likely in line for another Cy Young Award - for six runs and 10 hits in six innings. Edmonds hit a two-run homer off the 6-10 lefthander in the opening inning and Rolen added a long two-run shot in the fourth.

Johnson (0-1) fell to 0-7 in his last seven Division Series starts and, despite winning his five prior postseason appearances, sports just a 7-8 career postseason record.

"It appeared to me that mechanically he was rushing a little bit," Arizona manager Bob Brenly said. "When he does that, his velocity drops down. His slider is not quite as sharp as it usually is. They were a very unforgiving team to him tonight. He made some mistakes. They hit him hard."

"I didn't pitch as well as I should have, could have," Johnson said. "Just didn't make the quality pitches that you see over the course of a regular season. You need to make them in a five-game series because the game is so much more magnified."

Brenly and Johnson offered their takes on the superstar's struggles in the Division Series.

"I would guess it probably has to do with the opponent that he faces in the Division Series more so than just the Division Series itself," Brenly said. "It's a good ballclub over there. They had a real good game plan against him. ... all their hitters were concentrating on staying up the middle of the field, which is a great approach against Randy Johnson."

"I guess the numbers don't lie, Johnson said. "I guess I have some pretty bad luck (in the Division Series). There's no rhyme or reason. I couldn't tell you."

On Tuesday, Johnson was in trouble throughout and no match for St. Louis ace Matt Morris (1-0). The Cardinals righthander was a bit shaky early but allowed just two runs - one earned - and six hits in six innings. He walked two and struck out three.

"I think there was a point where it clicked," Morris said. "But having the runs, of course, made it a little easier. But I think from the fourth or fifth on, I was able to locate some fastballs and kind of settle down. I felt like I was getting a little stronger. But, you know, again, the offense gave me a nice cushion."

"He had the best stuff I've seen him have all year in the bullpen," Morris' batterymate Mike Matheny said. "He came in and he was fired up. He was excited how the ball was coming out of his hand."

After an off day on Wednesday, the series resumes Thursday with Arizona sending Curt Schilling to the mound. The Cardinals counter with veteran lefthander Chuck Finley.

"It's big (because) you always want to get that first game but we still have a big game on Thursday," Pujols said.

"I'm not depressed," Diamondbacks first baseman Mark Grace said. "There's hopefully three games left if we play well. We didn't expect to sweep these guys. If we are going to beat the guys we fully expect it to be a five-game series."

Fernando Vina opened the game by reaching on an error and one out later Edmonds drilled a homer over the right-center field wall. Edmonds, who hit two homers against Arizona in last year's Division Series, has six career postseason homers.

"It was big to try and get on the board early," Vina said. "When your facing Randy any run you can get early is big and fortunately that's what we did."

"I just tried to get a strike to hit," Edmonds said. "That's about all you can do against him. We did a great job of sticking to our game plan and making him pitch."

Arizona got back a run in the bottom of the first but had a potentially big inning cut short when Junior Spivey was thrown out at the plate on a single by Matt Williams.

The Diamondbacks drew even in the third on a two-out single by Quinton McCracken that scored Steve Finley but the game wasn't deadlocked long as St. Louis scored three times in the fourth.

Albert Pujols, who hit a two-run homer off Johnson in last year's Division Series, opened the fourth with a long triple and Rolen crushed Johnson's next offering over the wall in left-center field for a 4-2 lead.

"It's a great feeling," Rolen said of participating in his first postseason game. "Usually I am in Florida fishing. What I tried to do was take a few steps back, take a few deep breaths and try not to get caught up in the emotion and the adrenaline you are going to have. The home run helped me relax. I was just trying to put the ball in play up the middle and he got the ball up a little bit."

Edgar Renteria continued the fourth-inning onslaught with a single, stole second and scored on Mike Matheny's base hit.

A sacrifice fly in the sixth by Eli Marrero, who is 0-for-16 in postseason play, extended the Cardinals' lead to 6-2.

"You don't expect the game to go like that especially against a quality pitcher," Marrero said. "We went out there and battled and we got two early runs. Then we kept the momentum going."

Any chance the Diamondbacks had of getting back into the game was all but eliminated by St. Louis' big seventh inning. The Cardinals sent 11 batters to the plate, had just four hits but scored six times. Morris and Pujols had two-run singles in the inning.

Rolen made two of the three outs in the seventh.

The Diamondbacks bullpen continued to be a problem as Matt Mantei and Greg Swindell combined to retire just one batter and surrendered all six runs in the seventh.