The Phoenix Suns’ roster is filled to the rim.

With the latest addition of forward Cheick Diallo with a two-year deal, according to ESPN, Phoenix has 15 players.

HoopsHype estimated the Suns were around $9 million over the salary cap with a $4.8 million cap room exception available before adding Diallo.

So let’s take a deep dive over the next few days about how Phoenix could function under Monty Williams starting with its biggest free agent signing — Ricky Rubio.

Devin Booker is the team’s best player. No question.

Kelly Oubre Jr. is the top two-way player and Deandre Ayton could average 20 and 12, but Rubio might very well be Phoenix’s most important player this season.

“We have a guy in Ricky that’s going to make everybody more efficient than they have been,” Williams said Tuesday. “As a coach, you want to have someone on the floor who can manage a game from the point guard position and Ricky certainly does that for us.”

The Suns addressed their greatest need at point guard by signing the veteran from Spain to a three-year, $51-million deal. They ended up trading Josh Jackson to help get under the cap to complete the deal.

Phoenix probably overpaid for Rubio, but some outrageous deals were dished out in the biggest summer of free agency. The Suns couldn’t go through July without nabbing a quality, proven point guard.

They now have one.

Rubio has averaged 7.7 assists in his eight NBA seasons. He’s certainly a playmaker. That’s why Phoenix got him, but Rubio also must be a scoring threat.

He averaged a career-high 13.1 points two seasons ago in Utah and 12.7 last season. Gets to the rim, crafty and creative in transition, but is a career 32.2% 3-point shooter.

Rubio shot just 31.1% from 3 last season. Playing beside Booker, Rubio will get open shots and must knock them down at a higher clip from deep to keep defenses honest.

He also must be reliable on defense to help Phoenix switch on the perimeter and reduce dribble penetration. The Suns struggled keeping guys out the paint last season. 

Tyler Johnson will serve as a quality backup, but Rubio is the guy at that position who’ll “make everybody more efficient,” Williams says.

Phoenix’s franchise player is at the top of that list.

Booker was the Phoenix’s closer, leading scorer and top playmaker last season in averaging career highs in points (26.6) and assists (6.8 per game) but looked worn down at times from carrying those loads.

Some say that greatly led to his injuries as Booker averaged 35 minutes in the 64 games he played.

Only Bradley Beal, Paul George, James Harden, Russell Westbrook, Jrue Holiday and Damian Lillard logged more minutes per game.

Booker, only 22, will keep logging heavy minutes, but how he does it will be key. He can create his own shot all day in all types of ways, but less dribbling and more moving without the ball could make him more efficient.

Rubio can make Booker’s life easier by setting him up. That also requires Booker to trust Rubio will find him. Keep Booker in attack mode, but Rubio can help him and the team value every possession.

As big as the Rubio-Booker relationship is, the Rubio-Ayton pick-and-roll game could be a game changer.  

Booker averaged 19.6 shots in shooting 46.7% from the field.

Ayton averaged 12.3 shots on 58.5% shooting. That number needs to go up at least three attempts to better maximize Ayton’s ability.

He could get those extra shots in the pick-and-roll with Rubio.

That could lead to more free throw opportunities and getting in the bonus faster. Booker and Oubre will get theirs, but Ayton needs touches for floor balance.

Enter Rubio.

He made Rudy Gobert look good with drop offs at the rim and Gobert isn’t half the offensive player Ayton is. The Rubio-Ayton combination could be dynamic, especially with the threat of Booker and Oubre on the perimeter.

Rubio will have more responsibility in Phoenix than at any other point in his career. How he handles that will greatly determine if the Suns start turning the corner sooner than later.

Up next: Starting lineup, rotations and combinations.

Later on: The future.

Have opinion about current state of the Suns? Reach Suns Insider Duane Rankin at [email protected] or contact him at 480-787-1240. Follow him on Twitter at @DuaneRankin.

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