We can't say that enough; a pitcher must keep the ball on the ground as much as possible to be successful.  Jonathan Hale studied the question and arrived to some convincing conclusions and Rich Lederer looked at some of the best and worst in that category last season.

Here are the best and worst in GB% among starters this season:

Starters - Leaders

Fausto Carmona - 78.4%, .212 BABIP

If it was not for his 9 walks in 13 IP, his line would be excellent.  At least his heavy sinker his working, but according to the numbers, he's using his splitter a little more this season.  Last year, he finished with a 64.3 GB%.

Kason Gabbard - 71.4%, .297 BABIP

He is not a strikeout artist (far from it), but he knows how to effectively register outs and that's what's important for a pitcher.  He posted a 54.9 GB% in 2007 while not coming close to reaching the 90 mph mark on the radar with his heater and throwing his curve and changeup almost 45% of the time.

Tim Hudson - 68.3%, .203 BABIP

His 2006 season displeased him and the team.  Since then (and after an offseason of rigorous training and conditioning), he has 37 starts, 144 K, 55 walks and a whole lot of groundballs, with a 62 GB% in 2007, 5% more than the previous year and his best in his career.  With the 68.3% he currently presents, he's looking at another solid year and his renewed focus on his low-90s fastball and splitter have produced results the last 2 seasons.

Jose Contreras - 65.1%, .356 BABIP

The groundballs are there.  That's the good news.  When it comes to the walks, they are aplenty: 7 in 11 IP.  Ground ball outs will take you so far, but you have to couple that with control of the strike zone and command of your pitches.  Jose has been using his slider 30% of the time this season, almost twice as much as he did last season.  With a lively fastball like the one he possesses (and not even throwing it 50% of the time), he sould really come back to setting up his offspeed pitches more effectively, because the current approach is not working at all, except when it comes to ground balls.

Paul Maholm - 64.3%, .332 BABIP

The 25-year-old left-hander has clearly done his homework when it comes to reducing his walk rate (now at 2.61 BB/9) and keeping the ball down in the zone (above 50 GB% since he entered the majors).  This might me explained in part by his increasing reliance on his slider instead of his curve ball, which he tends to leave higher in the zone, resulting in more fly balls.  These fly balls still represent 28.6% of batted balls against him, but the line drives have taken a welcome hit, now at 7.1% of all balls put into play by opposing hitters.

He is also fooling hitters with this new approach, with a 9.58 K/9, by far his best showing in the majors.

Starters - Worst

Chris Young - 11.4%, .267 BABIP

Young loves Petco Park, because he is a reputed fly ball pitcher (54.3 FB% last season), but with 11.4 GB% in 2008, he's pushing the envelope. He had a 1.69 ERA (.498 OPS against) at home in 2007, but a below average 4.52 ERA (.651 OPS against) on the road.  He has yet to throw a curve ball this season and has replaced this pitch with more changeups (about 2.5% increase).  It's interesting to note that his fastball as lost about 2 mph of velocity on average in 2008.

Rich Harden - 21.7%, .272 BABIP

He has never been known to be a ground ball pitcher, but it is a trend that started last season, when only 38.3% of the balls hit against him went on the ground.  That's not his game, though, as his 12.27 K/9 in 2008 show (although the very small sample of innings makes it difficult to judge a trend.

Javier Vazquez - 25.8%, .377 BABIP

Vazquez has pretty much the same numbers that Harden presents when it comes to GB% in his career.  He has given up 25% of line drives in two starts, as he's putting more emphasis on his fastball, slider and curve so far in this campaign.

John Maine - 29.4%, .351 BABIP

His GB% has decreased every year since 2005, from 45.5% to 29.4% today.  He's been using his changeup a lot (1 out of every 5 pitch) in 2008 and if he's leaving it a bit high in the zone, the offering becomes very hittable for major league hitters who will try to drive it and not slash at it.  His line: 10 IP, 13 H, 5 ER, 8 BB, 6 K.

Nate Robertson - 31.3%, .449 BABIP

He's another pitcher that's seen his GB% decrease every year, but in his case, it's been a downward trend since his major league debut with the Marlins in 2002.  The fly ball rate has been increasing in tandem.  The southpaw has always been home-prone, but more balls in the air has not affected the number of them who reach the bleachers - quite the contrary.  He has been more effective in keeping the ball in the park, but he's been giving more headaches to the fans and coaching staff...that's all....