Pitches that will make or break 'pen

Tim Wakefield's knuckler is no more. Jonathan Papelbon's splitter has moved to Philly. And Dice-K's gyroball? Still waiting on that one.

With a revamped bullpen, there's a new set of pitches that will be key to the success of the Boston Red Sox.

Here's a look at each:

Bailey's career-making cutter

Flash back to 2008, when Andrew Bailey posted a 4.32 ERA in Double-A. One year later, he won American League Rookie of the Year.

The difference was one pitch.

Bailey learned the cutter during the 2008 season under the guidance of A's pitching instructor Gil Patterson. In 2009, opponents hit just .139 on at-bats ending in his cutter. In 2010, it was nearly as effective (.186).

But last season, Bailey's cutter wasn't quite the same pitch, as opponents hit .280. That might help explain why his ERA soared to a career-worst 3.24 ERA.

So what changed? For one, he lost some velocity on it. Bailey's cutter averaged 90.2 mph in 2009. Last year, it was down to 88.8.

More significant was a loss of precision. Over his first two seasons, 55 percent of Bailey's cutters were thrown in the strike zone. Last season, that was down to 45 percent.

Bailey needs to get his cutter back on track in order to return to All-Star form.

Melancon's two-strike curve

Last season, the eighth inning belonged to Daniel Bard and his 97 mph fastball. Get ready for a change of pace in 2012.

Mark Melancon is expected to handle setup duties. His signature pitch? An 82 mph curveball.

He used it on 27.3 percent of pitches last season. Among those who threw at least 1,000 pitches, only seven pitchers threw a higher percentage of curves.

Sure, Melancon can also bring a 93 mph fastball, but it's the curve that's his true out pitch. With two strikes, he threw the curve 50.7 percent of the time, the fifth highest rate in the majors.

Of his 66 strikeouts, 38 came on curveballs. Among relievers, only Jose Veras (64) and Sean Marshall (51) had more.

Of those 38 strikeouts on the curve, 28 came on pitches below the strike zone.

Indeed, Melancon's curve is at its best when it drops well below the zone. Opponents chased 48.9 percent of his two-strike curves that were out of the zone.

Aceves' elite fastball

Alfredo Aceves' average fastball was 92.2 mph last season. That's 5 mph slower than Daniel Bard, and just the 13th fastest among Red Sox pitchers last season.

So how is it that Aceves, who is a candidate to join the starting rotation this spring but could also land back in the bullpen, had arguably the best fastball on the team?

Last season, opponents hit just .195 on at-bats ending on his fastball. Among those who threw at least 1,000 fastballs, only Colorado's Guillermo Moscoso kept opponents to a lower average with his fastball.

Yet, that fastball accounted for less than half of Aceves' strikeouts. So how was it that successful? Opponents simply did not make good contact. Aceves had a 12.5 line drive percentage against his fastball, second lowest in the majors behind Ricky Romero.

That's a big reason opponents had a .211 batting average on balls in play against Aceves' fastball. The league average was .301.

Miller's hittable fastball

Take everything you just read about Aceves' fastball and flip it around for Andrew Miller.

Despite a 6-foot-7 frame that allows him to bring up to 98 mph heat from the left side, Miller's fastball was eminently hittable. Opponents hit .351 with a 1.014 OPS on plate appearances ending in a fastball.

Among those who threw at least 750 fastballs, only Esmil Rogers and Phil Coke were hit harder.

One of the key problems? Fastballs thrown right down the middle. Opponents were 17-for-29 (.586 BA) on Miller's fastballs in the middle of the plate. Take those away, and opponents would have hit .295.

Albers' disappearing slider

Entering August, Matt Albers was a surprising key cog in the Red Sox bullpen. Despite a career 5.11 ERA, he had a 2.09 ERA through four months of last season.

That's when his season fell apart.

Albers posted a 9.97 ERA over the final two months of the season. So what happened?

It starts with control of the slider. Consider that Albers features only two pitches. Losing accuracy on his slider was devastating.

Over the first four months of the season, he threw 46.2 percent of sliders in the strike zone. Opponents were held to a .265 batting average and .618 OPS on plate appearances ending in the slider.

When things fell apart, Albers' slider was in the zone only 32.7 percent of the time. And when it was in the zone, he tended to leave it right out over the plate. Opponents hit .500 with a 1.433 OPS on plate appearances ending in the slider.

When Albers missed, he missed badly. Of his sliders, 32.7 percent were considered non-competitive. That's the same percentage thrown in the zone during August and September. Over the first four months of the season, just 23.4 percent of sliders were non-competitive.

Morales with men on base

Franklin Morales was once the No. 2 prospect in the Rockies system, but never found consistency. One of the recurring problems was difficulty repeating his delivery from the stretch.

With that in mind, it's worth noting how much he struggled with men on base last season. Opponents hit .270 with a .926 OPS with men on base. With the bases empty, opponents hit just .211 with a .625 OPS.

The biggest issue was Morales' signature 95 mph fastball. With the bases empty, opponents hit .182 with a .611 OPS off his fastball. But when Morales had to throw that fastball out of the stretch, they hit .357 with a 1.282 OPS.

The pitch that might keep Bowden in the bigs

In the summer of 2009, Michael Bowden added a slider to his repertoire. Now, it's the pitch that might finally keep him on a major league roster.

The slider replaced the curve as Bowden's off-speed pitch, about 7 mph slower than his fastball.

Last year, that slider made Bowden a righty killer. In Pawtucket, righties hit just .121 against him.

That success carried over to his brief time in Boston, where righties hit .229. On at-bats ending in a slider, those righties were just 1-for-13 (.077).

Jeremy Lundblad is a senior researcher with ESPN Stats & Information. He provides statistical analysis for ESPNBoston.com.