Slugger J.D. Martinez eventually signing with the Boston Red Sox is not the inevitability it once appeared to be.

The outfielder is reportedly fed up with the team's inflexibility regarding its offer, and would prefer signing with a different team, sources told The Athletic's Ken Rosenthal. Martinez is also willing to hold out until he gets the deal he wants.

The Red Sox are believed to have put a five-year contract worth roughly $125 million on the table, and won't budge. It's become a "take it or leave it" scenario.

Despite the tumultuous nature of the negotiations, and both parties standing firm, the two sides are maintaining contact. The Red Sox, however, are looking at other options - both in free agency and via trade - in case a deal for Martinez fails to materialize.

"There are more free agents than we've ever dealt with," Red Sox president of baseball operations Dave Dombrowski said. "You take a look at your own players, analyze them, see how they're doing and say, 'Maybe this guy fits in better.' Or, 'Maybe we give this young guy a chance that we didn't anticipate giving a chance.' You're just going to have to experience it and know what all of your alternatives are at all times."

Martinez was one of two hitters to crank more than 30 home runs in the second half of 2017. Giancarlo Stanton went yard 33 times in 73 games with the Miami Marlins, while Martinez hit 31 in 66 games between the Detroit Tigers and Arizona Diamondbacks.