What makes someone a good hitter?  Seems to me that good hitting is a function of three things.  1) You hit the ball, when you swing.  2) You don't swing at bad pitches.  3) You hit the ball far, when you make make contact.  Let's look at Cleveland's lineup focusing on those three aspects.  (Note: I am using ISO to track power.  However, this seems flawed.  Does anyone have a better power tracking stat?)
_______________Contact %________O-Swing  %________ISO           
League Averages_____80.7___________26.2*___________.152*
Michael Brantley____                       
92.3                         ___________23.8                     ___________.081                  
Asdrubal Cabrera#                   ___85.3                         ___________25.0                     ___________.110
Shin-Soo Choo                         ______79.0___________                         
26.8                     ___________.184
Carlos Santana                         ______77.3___________                         
22.4                     ___________.207
Travis Hafner                             _______76.2___________                         
27.4                     ___________.172
Austin Kearns                             _______76.4                         ___________23.1                     ___________.132
Orlando Cabrera                       _____85.9                         ___________32.5                     ___________.091
Matt LaPorta                             _______
75.8                         ___________
33.7                     ___________.141
Jack Hannahan^_____                       77.3                         ___________20.1                     ___________.123 
Grady Sizemore^                       _____81.8__________                         
19.1                     ___________.204
Jason Donald _______                            77.9                         __________
36.3                     ___________.125
Travis Buck^                             ________78.6                         __________23.7                     ___________.174
Lou Marson                               _________85.0                         __________18.8                     ___________.092
Jayson Nix                                 _________77.8                         ___________33.3____________.172
Luis Valbeuna                           _______83.9                         ___________28.9                     ___________.121+
I have adjusted these numbers, when there is a statistical deviance.
* I averaged O-Swing rates and ISO from '07 - '10.  The 2010 O-Swing average was 29.3 and ISO was .145.
#This is Cabrera's career line.  His 2010 contact % was 88.6, O-swing % 27.4, and ISO .071.
^Hannahan, Sizemore, and Buck didn't play much (or at all) in 2010.  So, I used career numbers for them.
+Valbeuna's 2010 ISO (.065) was about half his career number so I used his career number.
Breakout candidates:
Michael Brantley - I did an extended analysis of
 Michael earlier.  At that time, I had just keyed into contact %.  Contact % keeps track of how often a player makes contact, when he swings.  So, please forgive me for not going ape shit over a 
92.1% contact rate over 446 PAs.  (Okay, it is not a huge sample.)  But this is an 
insanely high contact %.  The stat starts being tracked in '02.  Since '02, Ichiro has never had a season better than 91.7, and he averages 89.2. I have been searching hitters known for their contact skills, and I can't find a better %.  That comparison doesn't make Brantley a potential .340 hitter.  But mix in Brantley's +.300 BA in the minors, the second half of last year, and his rookie year in '09, everything points at this kid as a +.300 hitter.  Add the fact that Brantley doesn't swing at a ton of pitches outside the strike zone.  He has a 21.7 O-swing %.  This is a player that could easily have a .375 OBP.
Carlos Santana - Brantley is the darkhorse for break out player.  Your
 front runner is Santana.  Because no one keeps track of minor league contact % or O-swing %, I am focusing on a stat that gives me small samples for young players.  My gut screams breakout.  But nothing in the stats that I am looking at screams breakout.  I do like the minor league walk rates and the major league O-swing %.  But using contact, O-swing, and ISO as indicators, you have to put Brantley and not Santana as the lead breakout candidate.
Comeback candidate:
Grady Sizemore - This is almost a default pick.  
Will Carroll reports that there has never been a successful case of a player coming back from microfracture surgery.  
Never.  That is not encouraging.  So far, there is cautious optimism about Sizemore.  He seems to be making steady progress.  With the bad knee and in limited PAs, Sizemore had a 33.0 O-swing rate and 73.8 contact rate.  If Sizemore can get healthy, you should get a good OBP.  The career 19.1 O-swing rate is the best on the team.  It will be a wait and see about how much power Sizemore will have.  If he gets healthy, then he is a lead candidate for MLB comeback player of the year.
Bust candidate:
Matt LaPorta - No surprise here.  I wish the numbers were different.  It would make for more interesting analysis.  LaPorta is below league average in all three categories.  Watching him at bat this spring, you can feel the pressure he is putting on himself.  Hopefully, he can relax, and we will see a new hitter.  But these numbers are not encouraging.