The Chicago Cubs signed reliever Rafael Soriano to a minor-league contract on Monday in an attempt to solidify the back end of their bullpen, but it doesn't appear as if the club is done making moves.

Bruce Levine of 670 The Score reported the Cubs are "still looking for more relief help via the right trade" shortly after the team signed Soriano. Manager Joe Maddon went with a closer-by-committee system during the club's recent four-game set against the Washington Nationals and three different relievers recorded saves.

Closer Hector Rondon and setup man Pedro Strop struggled in the month of May and Maddon decided a change needed to be made. The Cubs' bullpen ERA (3.65) ranks 20th in the MLB and has only 14 saves (22nd) along with a 2.37 strikeout-to-walk ratio (21st). Are more experienced closers on their radar?

"The Cubs figure to be one of many teams hunting for bullpen help over the course of the summer, and they're at least the third team to reportedly be seeking trades for relievers in the past week alone," writes Steve Adams of MLBTradeRumors.com.

"Milwaukee and Philadelphia are the most commonly cited potential sellers, and each has high-priced assets that would be appealing to shed for a rebuilding club (e.g. Jonathan Papelbon, Jonathan Broxton and, perhaps, Francisco Rodriguez)."

We've previously touched upon a Papelbon-to-Chicago scenario, but it's unknown if the Cubs are willing to pay at least half of his $13 million salary this season and potentially take on his $13 million vesting option for 2016, which kicks in if he finishes 48 games this year. The veteran closer has finished 22 games so far to go along with a 1.13 ERA, 0.917 WHIP, 29 strikeouts and 12 saves in 24 games (24 innings).

The Phillies have had Papelbon on the trading block for quite some time now, but have been unable to work out deals with the previously interested Milwaukee Brewers and Toronto Blue Jays.

"If they trade him, they can move a lot of his salary, and there is value in that," one rival official told ESPN Insider Buster Olney. "But they can't expect another team to take the money and give up a prospect package of any real value. You can't expect both." 

As for Milwaukee, they're still among the worst in the MLB with their 22-37 record and are more than likely to be sellers at the trade deadline. One would assume they'd be willing to deal Rodriguez, who signed a two-year, $13 million deal this offseason, which includes a $6 million team option for 2017. He could provide the Brewers with a decent return since he owns a 1.23 ERA and 0.818 WHIP with 24 strikeouts and 12 saves in 22 games (22 innings) so far.

There's no question the Brewers are looking to get rid of Broxton, but there will certainly be a limited market (if any at all) for a reliever who is guaranteed $11 million through 2015 and has a 6.45 ERA and 1.522 WHIP in 24 games (22 1/3 innings).

Another option includes Cincinnati Reds' closer Aroldis Chapman, which would only occur if the Reds fall further out of the NL playoff race and are willing to sell their high-profile players at the deadline.

However, if Maddon's closer-by-committee system works nicely until Soriano reaches the majors then the Cubs may not be inclined to make a deal. Soriano has proven he's more than capable of assuming the closer role and he could be a good fit alongside Rondon, Strop and Jason Motte.