It's tough to remember a time when Rajon Rondo wasn't involved in trade rumors. As far back as the Celtics' championship season in 2008, they've seemed on the verge of unloading the polarizing point guard. It's never happened -- there were no deals to make them better in the past, and Rondo's value was hurt this season by his extended rehab from an ACL injury. But on Thursday, the Celtics drafted Oklahoma State guard Marcus Smart with the No. 6 pick, and with Rondo coming up on free agency next summer, it's never seemed more likely that he'll be playing elsewhere sooner or later.

During the Celtics' big-three era, before the exodus of Kevin Garnett, Ray Allen and Paul Pierce, Rondo had one of the best contracts in the league. A five-year, $55 million extension signed a year before a stellar 2010 postseason gave Danny Ainge a young cornerstone and arguably the most gifted passer in the NBA at well below market value. But with the Celtics in a full-on rebuild, armed with several future first-round picks but a roster in flux, paying Rondo max or near-max dollars this summer doesn't seem logical.

It doesn't help Rondo's future in Boston that Smart duplicates his skill set. Both are tenacious defenders -- playing them together would give the Celtics one of the toughest backcourts in the league to score against. But Rondo's never been a scorer, and while Smart is less of a facilitator and more of a finisher than Rondo, but neither of them can shoot. It's an awkward long-term fit.

Unfortunately for the Celtics, even if they decide to move Rondo, his value isn't as high as it used to be. He showed flashes of his All-Star form after returning from the knee injury, and it helps that his game has never relied on explosiveness or athleticism. But a cursory glance around the league reveals a lack of teams that seem like viable trade targets. It's not Rondo's fault, either: The league has simply never been deeper with quality point guards. Before Rondo's injury, he was clearly one of the five best players at the position. But he hasn't been healthy in so long that it's tough to put him in that company now, thanks to breakout seasons from Damian Lillard, Goran Dragic, Kyle Lowry and others. There are only a handful of teams for whom Rondo is a clear upgrade from their current starter, to the point that it would be worth giving up significant assets to acquire him.

The Kings have been linked to Rondo in the past, and new owner Vivek Ranadive would love to make a splash by adding another star to pair with DeMarcus Cousins. For reasons having mainly to do with his lack of size, the Kings have been reluctant to commit to Isaiah Thomas as their starting point guard. Thomas is a restricted free agent this summer, and the Kings have reportedly been looking into the likes of Shaun Livingston to replace him. It's a curious direction to take, as Thomas is one of the most offensively gifted point guards in the NBA. But Rondo may make more sense for Sacramento from a roster standpoint -- they just drafted sharpshooter Nik Stauskas with the eighth pick in the draft, and a facilitator and defender like Rondo at the point would be a nice fit next to him. Thomas, meanwhile, could fit better next to Smart than Rondo. Thomas' shooting and Smart's skill in attacking the rim would be an excellent fit, and Smart can cover for Thomas on the defensive end. Ainge would likely want second-year shooting guard Ben McLemore in a deal, but the pieces are there: McLemore, a signed-and-traded Thomas, and a future pick.

The Mavericks, having traded away starting point guard Jose Calderon to the Knicks last week, are currently looking at Raymond Felton as a replacement -- not ideal for a team hoping to contend, even in the unlikely event that they land a marquee free agent like Carmelo Anthony or LeBron James. A healthy Rondo would be able to shore up their perimeter defense, find Chandler near the basket for lobs, and set up Dirk Nowitzki with quality shots. Unfortunately, the Mavericks don't have much in the way of trade assets that would appeal to Ainge. Their best young prospect, Shane Larkin, was included in the Calderon-Chandler trade and wouldn't have been enough to entice the Celtics anyway. They own their own first-round picks going forward, but they're unlikely to be in the lottery in the next few years, and Ainge already has plenty of mediocre mid-first rounders from the Nets. If Rondo hits free agency, though, Dallas could be an intriguing destination.

With Steve Nash unable to stay on the floor since signing with the Lakers in 2012, Los Angeles is another team that could use an upgrade at the point. The Lakers are going to make a run for LeBron James and Carmelo Anthony in free agency, but nobody realistically expects either one of them to sign with a team this depleted of talent. A trade with the Celtics is a non-starter, unless the Lakers wanted to give up lottery pick Julius Randle, which is tough to fathom. They owe their 2015 pick to the Suns if it falls outside the top five, and they're unlikely to want to unprotect it to trade for Rondo. They have no other assets of note.

At a time when it makes more sense than ever for Ainge to trade Rondo, there's simply no clear destination for him, and his value is an unknown. Fewer teams each year have a need at point guard, and the ones that do don't have anything approaching the kind of assets Ainge would ask for in return. Even a Kings trade is risky, unless Sacramento receives assurances that Rondo won't walk next summer, and at this point, nothing about their roster or recent track record gives him reason to commit. Through no fault of his own, the trade market for Rondo may simply have passed him and the Celtics by.