On Wednesday, the Baltimore Orioles traded shortstop Manny Machado to the Los Angeles Dodgers.

Machado's name had been a fixture in trade rumors dating back to last winter due to his impending free agency as well as the Orioles' inability to retain his services or compete this season. Trading Machado had become a matter of if rather than when.

With "when" passing, it's time to face reality: Machado is no longer a walking trade rumor. The passage of time demands succession, however, meaning someone must fill the void. Who? In our estimation, Machado's heir could be Colorado Rockies third baseman Nolan Arenado.

Let's count the reasons.

Nolan Arenado is a star -- one who will demand a large contract in free agency. USATSI

Arenado is nearing free agency

If it feels like Arenado has been around for a while, it's because he has been. He debuted in 2013 and has since blossomed into one of the National League's top performers.

Along the way, Arenado has accumulated more than five years of big-league service time. For those unfamiliar with the concept, "service time" is how baseball determines who is and isn't eligible for free agency. A player needs more than six years in order to hit the open market, with each "year" consisting of 172 days.

Arenado, then, will become a free agent after the 2019 season.

In certain circumstances, a player's forthcoming date with free agency isn't a huge deal. The Rockies, for instance, found a way to re-sign Charlie Blackmon during his walk year.

With Arenado, there's one big reason to think an extension is unlikely: the Rockies' efforts to lock in Arenado over the years have came up short. If Arenado wants to force an extension, he could, but so far he seemingly hasn't felt the desire to.

The Rockies could be nearing their payroll limit

Even if Arenado was willing to give the Rockies a discount, it's unclear how big one of they would require before they could make a competitive offer.

Colorado entered the season with a franchise-high $136 million payroll -- or about $9 million more than they had spent in 2017, and $24 million more than in 2016. How much higher can that figure climb? Only management knows. Still, if the answer is "not much," then the Rockies will face some difficult decisions heading forward.

Consider that, even without an Arenado extension, the Rockies have $84 million in guaranteed salary for 2019 and another $70-plus million in guaranteed salary for 2020, per Cot's Contracts. Those figures don't factor in potential external additions or arbitration prizes (including Arenado's for next season, which should top $20 million).

Maybe ownership would be willing to stretch in order to retain their homegrown stars. But there's no sense banking on it.

Colorado's division and pennant aspirations are limited

Presuming Arenado doesn't sign an extension, this factor is the one that's most likely to determine whether he's traded or permitted to walk as a free agent. Unfortunately for the Rockies, it's easy to see a path leading either way.

The Rockies made the playoffs last season (albeit just the Wild Card Game) and are two games back in the wild-card hunt and in the division this season. SportsLine gives them a 29 percent shot at cracking October. That's a fair percentage, but it's not a great one -- not when it's hard to see the Rockies leaping over the logjam ahead of them.

Who knows what the muddled National League will look like in a year's time. From here the Chicago Cubs, Los Angeles Dodgers, and Milwaukee Brewers don't appear to be going anywhere. The Atlanta Braves and Philadelphia Phillies seem to be on the upswing. It's at least conceivable that the Washington Nationals and San Francisco Giants remain competitive. And that's without mentioning the Arizona Diamondbacks or St. Louis Cardinals.

The Rockies may find their way into this October. Heck, they might do it next year, too. Anything can happen … but it's hard to see them improving enough to win the division or break away from the pack. That, plus the aforementioned factors, are why we're almost certain to see Arenado pop up in myriad trade rumors over the course of the next 12 months.