OKLAHOMA CITY – It didn't take John Danks long to figure out the differences between Double-A Frisco and Triple-A Oklahoma when he was called up in late June.

He boarded a commercial flight instead of a bus for his first road trip. He walked into a larger home clubhouse. He pitched in a bigger ballpark.

Oh, and he noticed the hitters are a whole lot better.

"You can't make many mistakes here," said Danks, a left-handed pitcher. "If you're up in the zone, you'll get hit. I could throw 12 horrible curveballs in Frisco and guys would swing at them. They don't up here. You have to place the ball better."

Danks, one of the youngest pitchers in Triple-A at 21, is learning all about it. He can use Edinson Volquez as a study guide. Volquez has spent the entire season in Oklahoma working through the challenges of succeeding this close to the big leagues.

For Volquez and Danks, two-thirds of the Rangers' celebrated "DVD" pitching trio (along with Thomas Diamond, who is in Frisco), this is the final test before they can join the big-league staff.

So how close are they?

"I think they are just not quite ready," Oklahoma pitching coach Andy Hawkins said. "There are things lacking in their games right now that will be exposed at the next level. But they can compete at this level, and this is a good place for them to be. They're going to be ready soon, just not quite yet."

Rangers general manager Jon Daniels said he doesn't want either pitcher to come up until he can contribute and succeed.

Daniels said before the trade deadline that he couldn't see trading either for a rent-a-player. And though both were mentioned in rumors, neither was dealt.

TY RUSSELL/Special Contributor

Edinson Volquez

"Anything can happen, but my hope and expectation is that both of them are in our rotation in the future," Daniels said. "I think we'll know when they are ready to really help us. Right now, they can stay and keep working in Oklahoma."

The Rangers keep a close eye on two of their prized prospects. Minor league pitching coordinators Rick Adair swings by a few times a month to check on them. And the team files reports to Daniels, Rangers manager Buck Showalter and pitching coach Mark Connor after every start for evaluation purposes.

Their pitching styles are different, but they have the same problem: fastball command.

Volquez sports a 94-95 mph fastball. He has what scouts call a "plus" change-up, meaning it's a major league-quality pitch. The severe change in speeds has helped him stay in the top three in strikeouts in the Pacific Coast League all season. But he's also been near the top in walks.

"The walks are going to be accentuated in the big leagues," Hawkins said. "He has all kinds of arm strength but has to figure out the command problems."

Volquez, 23, got a taste of the majors in 2005. He was 0-4 with a 14.21 ERA in six games (three starts). Daniels acknowledges that the club rushed Volquez to the big leagues.

But he and the Rangers coaching staff hope Volquez's happy-go-lucky attitude allows him to forget about his troubling major league debut quicker than most would.

"He's laid-back, and that can be an advantage or a disadvantage," knuckleball pitcher R.A. Dickey said. "You hope that he takes it seriously enough. I think he does. He came up and got some humble pie, like we all do, and didn't pout about it when he could have. That's a big step."

Danks also has had command issues. Although he isn't walking as many batters as Volquez, he's leaving too many fastballs up in the strike zone, and hitters are belting them. The young left-hander, mature beyond his years, is intense and focused on figuring it out. Danks is a grinder with a fierce game face.

Danks doesn't throw as hard as Volquez. His fastball is more in the 88-92 mph range. But he has a good change-up and is refining his curveball. He has confidence in all of his pitches. His goal is to finish better than in 2005, when he was 4-10 with a 5.49 ERA in Frisco from June to the end of the season.

But Danks is not having a good second half. Since his start the day before the All-Star break, he is 0-2 with a 9.18 ERA in four starts. He has walked nine and struck out 20.

BRAD LOPER/DMN

Since his call-up from Frisco in late June, left-hander John Danks has gone 2-4 with a 5.90 ERA for Triple-A Oklahoma.

"I've been terrible lately up here, but I feel like it won't turn into the second half I had last year," Danks said. "I feel like I'll bounce back and that I'm in better shape to do that. I want to do my job, pitch well and put some pressure on them to move me up."

Both pitchers work on their own schedules between games. Danks usually throws one bullpen session and doesn't do as much with his arm during his four off days. Volquez threw two sessions before the All-Star break and has dropped back to one now that he's thrown more than 100 innings.

"We do what's best for each guy," Hawkins said. "As different as they are, they both have a great work ethic. They come to the park wanting to get better. And they have. They have a great future."

That future gets closer and closer.

E-mail rdurrett@dallasnews.com

Age: 23

Obtained: Right-hander signed as free agent in 2001.

2006 statistics: 6-6, 3.21 ERA in 21 starts (120 2/3 innings) for Oklahoma. Has 72 walks and 130 strikeouts.

Pitches: Two-seam and four-seam fastball, curveball, change-up

What he does well: Has a strong arm, capable of throwing 100 mph. He has a great change-up.

What needs improving: Command. He walks way too many batters, leading to big innings and high pitch counts. He has to learn to throw fastballs in the right spots consistently.

Age: 21

Obtained: Left-hander was Rangers' first-round pick in the 2003 draft.

2006 statistics: 2-4, 5.90 ERA in eight appearances (seven starts) for Oklahoma. Has 41 strikeouts and 17 walks.

Pitches: Two-seam and four-seam fastball, curve, change-up

What he does well: Mixes speeds and pitches well. Confident enough to throw all of his pitches in a variety of situations. Has worked hard to make his change-up an effective pitch.

What needs improving: He has to get more consistent throwing the two-seam (sinker) away from a right-hander and the four-seam away from a left-handed hitter. Both pitches are key to getting outs. He also needs more work on his curveball.