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There is always plenty of baseball to be played in summer. And where there is baseball, there are baseball rumors.

The MLB trade deadline is July 31, and the trade whispers are developing into full-on shouts as teams either position themselves to acquire long-term prospects or gear up for a run at the postseason.

Playoff contenders like the Toronto Blue Jays and Milwaukee Brewers are looking to add the final pieces to the puzzle over the stretch run, while cellar-dwellers like the Arizona Diamondbacks and Chicago Cubs could ignite a fire sale in the coming weeks.

The market will only get busier from here on out, so let's take a look at some of the bigger names rumored to be on the move this summer.

Is Jason Hammel the Most Sought-After Pitcher In the League?

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Chicago Cubs starting pitcher Jason Hammel is having a career year of sorts, and word is that teams around the league are taking notice of his value.

The lanky right-hander is 7-5 with a 2.98 ERA and 97 strikeouts. He is showing much greater control than in previous years, walking just 21 batters in 102.2 innings pitched thus far. It's possible Hammel is the most popular pitcher on the trading block, ahead of players like David Price and current teammate Jeff Samardzija.

“You could argue that Hammel is the most sought-after player, positional or pitcher, in the trade market right now,” a source told The Boston Globe's Nick Cafardo.

Hammel's deal expires at the end of the season; he could be the perfect target for a team looking to bolster its rotation for a playoff run.

According to CBS Sports' Jon Heyman, the Toronto Blue Jays may be interested in Hammel:

The first-place Blue Jays keep getting connected to ace Cubs righthander Jeff Samardzija(it's been going on for years now, it seems), but the sides have yet to make new proposals, and while the Jays will talk about Samardzija, sources suggest they are ultimately much more likely to trade for Samardzija's teammate Jason Hammel or another comparable rental starter.

The New York Yankees are another team that could be interested in Hammel's services. CC Sabathia is still recovering from a knee injury, and there is no telling what form he might be in when he returns. Prior to his injury, Sabathia was 3-4 with a 5.28 ERA in eight starts.

Gene J. Puskar/Associated Press

General manager Brian Cashman has stated he is looking to add players to the squad.

"I’m looking to make some additions if I can,"Cashman said, via the New York Times' Zach Schonbrun. “I’d like to try to do a few things before those guys get back, if possible. But I’ve already been trying. There’s a reason we haven’t done anything; it’s not because of a lack of phone calls. We’ll see."

The Yankees are third in the AL East after attempting to rejuvenate their roster with the likes of Jacoby Ellsbury and Brian McCann in the offseason. They have a tendency to lose big at times; Hammel could provide some much-needed stability behind ace Masahiro Tanaka in the rotation.

Rickie Weeks Fielding Interest Around the League

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The Milwaukee Brewers are 51-33 and battling to maintain their lead in the National League Central. It's possible the team could go for a pitching boost to prevent the ignominy of a late-season collapse, but it remains to be seen just how the Brewers will go about bringing in a solid starter. Second baseman Rickie Weeks could be part of a possible deal.

According to Tom Haudricourt of the Milwaukee Journal-Sentinel, Brewers general manager Doug Melvin said he listened to inquiries from several teams about Weeks' services, although no team has come up with any specific offers.

Weeks has been with the Brewers for his entire MLB career, but his play has fallen off considerably in recent years.

Rickie Weeks MLB Stats, 2010-2014 Season Games Batting Average Hits Home runs RBI On-base Percentage 2010-2011 118 .269 122 20 49 .350 2011-2012 157 .230 135 21 63 .328 2012-2013 104 .209 73 10 24 .306 2013-2014 64 .265 35 3 15 .331 ESPN.com

No longer of critical value to the team, Weeks could be thrown in as a potential deal-sweetener if the Brewers look to bring in a high-caliber pitcher. Melvin has stated he won't be trading away blossoming youth to get what he needs.

"We're not going to deal the young impact player to help our big club now," said Melvin, via Haudricourt. "It's going to be tough to do that. I think we do have a lot of players in our system that will play in the big leagues."

If Melvin can rekindle a conversation with one of the teams that called about Weeks, he might create an opportunity to solidify his team and add depth before the postseason.

Brandon McCarthy Aware He Could Be Traded

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The Arizona Diamondbacks are currently at the bottom of the NL West, and they could very well look to sell off expendable assets and prepare for an overhaul.

Starting pitcher Brandon McCarthy is in the second year of a two-year, $15.5 million deal and could provide a boost to teams looking for help at the back of the rotation. McCarthy may have an inside line on his fate, as he seems resigned to the possibility of a trade:

Via Fox Sports Arizona's Jack Magruder:

It certainly seems likely, but if I am still here at the end of September, then great. It is a place I enjoy. At this point, you become an asset the other way. Right now as a Diamondback, sometimes your best value is your future value and what they can get for you. I totally understand that side of the game. You accept it as reality, but it is not something I sit and worry about all the time, check every rumor. Just let it happen, and when I get a phone call and that happens, there you go.

The Diamondbacks could have a bit of a hangup in a potential deal. ESPN's Buster Olney tweeted about the contract issue:

Whichever team takes a stab at McCarthy might have to sweeten the pot to make the deal worth it for the D-backs from a financial standpoint. Of course, it's hard to see how much added value the Diamondbacks could get for a pitcher with a 5.11 ERA on the season.

The 30-year-old did have one of his best starts of the season Friday, allowing one run over seven innings in the Diamondbacks' 2-1 victory over the admittedly light-hitting San Diego Padres. McCarthy's current output doesn't warrant the amount of money the D-backs are paying him, so the team could be anxious to see him go before the deadline.