Now is the time to try and acquire a big bat or pitcher before they take off. Now is the time to sell players that are on hot streaks before they cool off. At the end of each month, fantasy owners look at their teams and how each player has performed over the last month.

This is when players get dealt if they had a bad month or had a hot month that nobody saw coming. Now is the time to start talking with other owners and trying to make a deal to improve your team. If an owner is an unfortunate owner of Grady Sizemore (on the DL and will have knee surgery) or Kendry Morales (fractured foot after home run celebration), then now is the time to talk to them about dealing a replacement for them.

Here are players to buy and sell:

Catcher

Buy:

Mike Napoli (C LAA)- I discussed about picking up Napoli after his recent hot streak, but Napoli is showing no signs of slowing down. Now that Kendry Morales is possibly out for the year, the Angels are forced to move him to play him at first base once Jeff Mathis comes off the DL.

Napoli is on pace for over 30 homers this year and is one of the top hitting catchers in the league. If he is on the waiver-wire, pick him up or else try and do what you can to deal for him if you don’t have Joe Mauer or Victor Martinez. For some reason he’s still only 65 percent owned in Yahoo leagues.

Sell:

Rod Barajas (C NYM)- Barajas is having a career year so far with eleven homers and 31 RBIs. Odds are he won’t keep up this rapid pace. He’s 34 years old and has never hit more than 21 homers in any season. Now is the time to sell Barajas.

First Basemen

Buy:

Prince Fielder (1B MIL)- Fielder is struggling out of the gate and now is the time to do what you can to acquire him. See if you can dangle a David Ortiz or Troy Glaus and somebody for him. Both Ortiz and Glaus are off to great starts, but are great trade bait while they are hot. Packaging a few of these guys for a guy like Fielder is the type of deal you have to make if you don’t have a great first baseman.

Sell:

David Ortiz (1B BOS)- Ortiz has never had a better month than in the month of May. He’s never hit more homers in any other month. The problem with Ortiz is that he still can’t hit lefties and is prone to hot and cold streaks.

I’m not saying trade him for anything, but packaging he and another player for a top first baseman might be the best thing to do with Ortiz. He’s not getting any younger and the Red Sox won’t hesitate to bench him for his cold streaks.

Second Basemen

Buy:

Brandon Phillips (2B CIN)- Phillips is starting to heat up after a strong May in which he hit .310 with five homers, five stolen bases, 25 runs, and nine RBI. Now is the time to try and acquire him.

Sell:

Kelly Johnson (2B AZ)- Johnson is starting to cool off after a hot start. Johnson is a very streaky player and frustrating player to own. He will probably come close to hitting 25 homers, but since he already has 12 he’s not going to be hitting too many more. Now is the time to shop him around and see what you can get for him.

Third Basemen

Buy:

Pablo Sandoval (1B/3B SF)- Sandoval struggled in May, but is too good not to turn it around. See what it takes to try and get him, because when he gets hot, you will want to own him. He is very streaky and can be frustrating at times, but if you don’t have a top first or third baseman then it can’t hurt to try and acquire the “Kung Fu Panda.”

Sell:

Placido Polanco (2B/3B PHI)- Polanco has cooled off after his hot start and is really only good for runs and batting average. He won’t do much else batting in the No. 2 hole. He’s valuable, but see what you can get for him before he cools off entirely.

Shortstop

Buy:

Ben Zobrist (2B/SS/OF TB)- Zobrist was off to a terrible start, but is now finding his groove. He went from batting .241 in April to .356 in May. He’s so valuable since he can play three positions and is somebody to target in trades while you can still get him.

Sell:

Alex Gonzalez (SS TOR)- This seems like an easy one to predict, but if there are any owners searching for a shortstop then see if they want Gonzalez. He may not bring back much value, but swapping him for a struggling player that is on the verge of breaking out is the move to make with Gonzalez. He won’t keep up his surprising start to the year.

Outfielders

Buy:

Justin Upton (OF AZ)- There could never be a better time than now to try and acquire Upton. He got off to an ugly start, but is showing signs of turning things around after batting .279 in May with four homers and 15 RBI. He is still striking out too much, but he’s worth trying to acquire. He will have a huge year when it’s all said and done.

Sell:

Alex Rios (OF CWS)- Rios is the number two ranked player overall over the last month and now is the time to shop him around. Rios has always had great potential, but always seems to disappoint. Rios might finish with his best numbers yet, but his value could never be higher. If you can get a more reliable hitter like an Adam Dunn then you have to pull the trigger.

Starting Pitchers

Buy:

Jonathan Sanchez (SP SF)- Sanchez has gone under the radar and is quietly having his best start to the season yet. He has cut down on his walks dramatically with only 29 in 62 innings pitched. He is still striking a lot of batters out with 63. His value is down mainly because of a few bad outings and the Giants abysmal offense, but now is the time to acquire him. He has the potential of being an ace so get him before he really breaks out.

Sell:

Jeff Niemann (SP TB)- Niemann is a solid pitcher, but he is not a great fantasy starter since he doesn’t get a ton of strikeouts. He has been very lucky with a .209 BAA and will probably end up with numbers similar to last year (3.94 ERA). At some point the luck has to run out so shop him around to see if anybody pulls the trigger and accepts a deal.

Relief Pitchers

Buy:

Billy Wagner (RP ATL)- Now that the Braves are in first place, Wagner is getting more save opportunities. After getting two saves in April, he dominated in May with five saves, 19 Ks, and only three walks. Buy Wagner now before people start to remember how dominant he can be.

Sell:

Octavio Dotel (RP PIT)- The Pirates are everybody’s favorite sellers at the trading deadline so you can expect them to sell their top players once again. Dotel is no exception and will most likely get dealt to a contender at the deadline as a set-up man.

His value is very high right now since he has salvaged his tough start with seven Saves in May and a 0.90 ERA, 14 Ks, and six walks. If you own Dotel, pick up his potential replacement, Evan Meek, and deal him to somebody who is desperate for saves.

Read more MLB news on BleacherReport.com