(SportsNetwork.com) - Six races down and 20 to go before the regular season ends in the Sprint Cup Series.

It's still a long way to go before the 16-driver field is determined for the Chase for the Sprint Cup championship, There are five drivers -- Denny Hamlin, Kevin Harvick, Jimmie Johnson, Brad Keselowski and Joey Logano -- virtually guaranteed of making this year's playoffs in NASCAR's top series after each one of them has won a race this season.

With 11 positions still up for grabs in the Chase field, who has a good chance of making it in and who doesn't based on performances early in the season?

Harvick, the defending Sprint Cup champion, has two wins, while Hamlin and Johnson as well as Team Penske drivers Keselowski and Logano have one victory each. Hamlin became the most recent one to join the Chase party with his win this past Sunday at Martinsville. It was the first time he, Joe Gibbs Racing and Toyota went to victory lane for a Sprint Cup points race since May 4, 2014 at Talladega.

"It's a big win for Gibbs and Toyota," said Hamlin, who moved from 14th to seventh in points. "It's been a rough year for both of us. We're just not used to not having success, especially with the resources that we have. Boss man (team owner Joe Gibbs) expects a lot from us, and we expect to be in victory lane and be up front. Even though it doesn't cure things, it makes things better.

"We've got some kinks in our team right now, but like (crew chief) Dave (Rogers) says, this buys you months of time to get everything worked out and get all the kinks worked out because we know we can go on a championship run."

Positions 1-15 in the Chase are determined by the drivers with the greatest number of wins after the regular season concludes on Sept. 12 at Richmond. The 16th spot is reserved for the points leader if he or she does not have a victory.

Last year, 13 drivers scored at least one win during the regular season to qualify for the Chase. Greg Biffle, Matt Kenseth and Ryan Newman did not have a victory but made it into the field based on points.

Right now, Martin Truex Jr. is the highest-ranked driver in points without a victory. Truex, currently third in the standings, has finished no worse than eighth this season. He placed sixth at Martinsville despite having a loss of power steering during the race.

"It's awesome," Truex said of his six-race streak of finishing in the top 10. "I can't say enough about the team. To battle like we did (at Martinsville), we showed that we never give up. We haven't all year long. It feels good to have another good run at one of my worst racetracks."

Truex only had five top-10 finishes for the whole season last year. He placed 24th in points in his first season driving for Furniture Row Racing, a single- car team in Sprint Cup.

Harvick, the current points leader, and Logano, presently second in the standings, are the other drivers who have finished in the top 10 in each of the six races this season. Keselowski, fifth in points, has five top-10s.

Kasey Kahne (fifth in points), Paul Menard (sixth) and Dale Earnhardt Jr. (eighth) are all off to good starts this season. Newman had been sixth in the standings, but he was docked 75 points as part of his team's penalties for tire manipulation in the March 22 race in Fontana, California. Newman is now ranked 26th. NASCAR issued the penalties to his No. 31 Richard Childress Racing team on Tuesday afternoon.

Earnhardt, though, dropped five spots in the rankings after his 36th-place finish at Martinsville. He dealt with a broken shifter early in the race and then was involved in an accident just before the halfway point, which put him in the garage briefly for a damaged radiator. Earnhardt won at Martinsville for the first time last October.

Other drivers who are presently ranked in the top 16 in points are: Aric Almirola (ninth), Kenseth (11th), David Ragan (12th), Casey Mears (13th), Jamie McMurray (14th), Danica Patrick (15th) and Jeff Gordon (16th). Johnson dropped to 10th in the ranking after his 35th-place finish this past weekend.

Ragan continues to drive the No. 18 Joe Gibbs Racing car in place of the injured Kyle Busch. It's not known yet when Busch will return to racing after he fractured his right leg and left foot during an accident in the Xfinity Series season opener at Daytona in February. He has made the Chase in each of the last five seasons.

Ragan has never qualified for the playoffs and this might be his best shot at doing so while driving the 18. He scored his first top-10 finish of the season with a fifth-place run at Martinsville.

"I feel like we've underperformed the last three or four weeks," Ragan said. "A lot of it has been just mistakes on my behalf. We've been really good. We've had some good speed, and we've had top-10 cars, but we just haven't been able to have a good entire weekend. We put together a good race (at Martinsville), and that's most important."

When Busch is medically cleared and hops back into his car, Ragan will return to Front Row Motorsports and resume his driving duties in the No. 34. Ragan's last Sprint Cup win occurred at Talladega two years ago, in his second season with Front Row.

Gordon had a rough start to his 23rd and final season in the series, finishing 33rd at Daytona and 41st at Atlanta due to accidents. After placing 18th at Las Vegas, Gordon has recorded three straight top-10 finishes. At Martinsville, he held the lead with less than 40 laps to go but was penalized for speeding onto pit road during the last caution. He ended up finishing ninth.

"It didn't fare well for us, and that's our fault," Gordon said. "We just had some things that didn't go well for us, and we need to perform at a higher level."

Gordon, a four-time series champion, has moved up 14 positions in the point standings since Las Vegas.

Those drivers who are struggling this year include Carl Edwards and Tony Stewart.

Edwards, who lost the 2011 championship to Stewart in a tiebreaker, has yet to record a top-10 finish this season and sits 17th in points. This is his first season driving for JGR after spending the last 11 years with Roush Fenway Racing.

Stewart has accumulated just 87 points for the season, which ranks him 32nd. He had finished 30th or worse in the first four races before placing 14th in Fontana and then 20th at Martinsville. It's been nearly two years since Stewart has won a race in the series.

Kurt Busch missed the first three races when he was suspended by NASCAR due to domestic violence allegations, but Busch is eligible for the Chase if he were to win during the regular season or collect enough points to earn a spot in the field. The Stewart-Haas Racing driver has moved up to 24th in points after top-five finishes at Phoenix and Fontana and then a 14th-place run at Martinsville.

Sprint Cup takes its first break of the season this Easter weekend and then returns to action the following week at Texas.