The anticipation for a TV series going into its second season isn’t unlike that of an athlete coming out of his rookie year: There’s reasonable expectation of some kind of progression now that enough time has gone by for the kinks to have been worked out. Which makes it all the more disappointing that a show set in the world of pro football, HBO’s “Ballers,” doesn’t seem to have elevated its game in its sophomore outing.

The lingering problem is one that plagues many teams: no matter how good a franchise player is, winning is difficult without at least some strength in the supporting cast. Unfortunately, “Ballers” rests almost entirely on the mountainous shoulders of A-list attraction Dwayne Johnson.

That’s odd considering HBO knows all too well how much power its comedies draw from deep benches, from the ensembles at “Veep” to “Silicon Valley.” The last comedy “Ballers” creator Stephen Levinson parked at HBO, “Entourage,” may not measure up to the channel’s new generation of half-hours, but that show understood how important it was to sprinkle memorable characters even into minor roles.

But as was the case in its first season, there’s noticeable drag in the story every moment “Ballers” spends away from protagonist Spencer Strasmore (Johnson), a former NFL lineman who brings the same competitive spirit that made him successful on the field to his second career as a financial advisor to football players. Maybe he’s too driven, as the second season suggests: Strasmore finds himself in a feud with the top dog in his new business (new series regular Andy Garcia) after poaching one of his clients. A brawl with that client also leaves Strasmore with a serious hip injury he begins self-medicating by abusing prescription painkillers than get the surgery he needs.

If that sounds familiar to those who saw “Ballers'” first season, it’s because Johnson spent much of those episodes pill-popping in fear he suffered long-term damage from too many traumatic brain injuries during his playing days, only to eventually get a clean bill of health from his neurologist. While it’s a nice touch on a show that deserves points for authenticity that a retired NFL star would be dealing with lots of health problems, the storyline plays out in a pretty repetitive rhythm to the “Ballers'” rookie season.

If all these plots don’t sound particularly knee-slapping, that’s because the show actually straddles the line between comedy and drama more than most HBO half-hours. A lot of credit for that balancing act should also go to Johnson, who acquits himself nicely in either mode. The role seems as tailor-made to fit him as the incredible array of power suits he wears in each episode, ensembles deserving of their own Pinterest page.

Levinson makes “Ballers” just as much a visual treat in its depiction of Miami’s luxe fashion, architecture and nightlife as he did for “Entourage” in Los Angeles. But all the eye candy in the world can’t compensate for the show being too dependent on Johnson.

As Strasmore’s antic partner, Joe Krutel, Rob Corddry isn’t given enough to do beyond banter wittily with Johnson. He should be “Ballers'” scene-stealer, akin to Jeremy Piven in “Entourage,” but barely gets his own storylines in season 2.

He’s not alone; the screen time without Johnson seems to have been indiscriminately divvied up among a group of characters that just don’t register. While more grizzled and gravel-voiced than ever, Garcia is unremarkable. Returning series regulars Omar Miller, Troy Garity, Dulé Hill and Donovan W. Carter are shuffled from one forgettable B story to the next. London Brown, who was at least a good foil for Johnson in the first season as a trouble-making hanger-on to one of Strasmore’s star clients, continues to get significant screen time even though resolving their beef makes him far less compelling.

And what should be a breakout vehicle for John David Washington, who has the looks and charm of his legendary father Denzel, as a talented but emotionally erratic wide receiver, just isn’t, though he may be the only example of a character who seems more interesting in the second season. His boring relationship struggles have been traded in for a more compelling storyline about being courted by various teams in free agency, nicely capturing the absurdity of how excessively pro sports overindulges in athlete recruitment.

And as for “Ballers'” female characters, there’s not enough there to even criticize.

“Ballers” should be the kind of show in which viewers come for Johnson but stay for at least one character from some hilarious assortment of options. But the only one that comes close to qualifying is Corddry.

If a third season happens, HBO might want to take a cue from “It’s Always Sunny in Philadelphia” and bring in a mid-run ringer as the FX series did with Danny DeVito. One suggestion: find a way to write more for Christopher McDonald, who plays a slick team owner. He deserves more than the 60 seconds he gets in the first five episodes of the season.

Think of “Ballers” as a .500 team in TV’s comedy standings, which doesn’t mean it’s a bad show. To the contrary, what’s frustrating is how it seems just a new player or two away from a winning recorD.

(Series; HBO, Sun. July 17, 10 p.m.)