The 49ers need a starting left guard and could draft Jonah Savaiinaea in Round 2. Here’s why:

Aaron Banks recently signed a four-year, $77 million deal with the Green Bay Packers. The 49ers originally drafted him in the second round of the 2021 NFL Draft (pick No. 48). And they drafted him to replace Laken Tomlinson, who had been picked in Round 1 of the 2015 NFL Draft by the Lions.

Banks, Tomlinson and Savaiinaea are similar. They’re all big guards who weigh more than 320 pounds. And they’re all better at pushing forward than moving side to side. Which means they don’t seem like good fits in Kyle Shanahan’s offensive system, but they are.

Kyle Shanahan’s system is predicated on running the outside zone play. But they run that concept mostly to the right side of their formation. That’s where they generally line up George Kittle, the best blocking tight end in football, who can seal the edge and create huge gains up the sideline.

It’s also where they have Dominick Puni, one of the quickest and most agile guards in the league. He’s great at executing reach blocks, ones that require him to outflank a defensive lineman and wall him off like he’s setting a violent moving screen in basketball.

Meanwhile, the 49ers like to run their inside zone runs to the left side of their formation. That’s where Trent Williams and Aaron Banks played side by side for years. For an inside zone run, those two would double-team one defensive tackle and push him as far backward as they could. That’s why they want a big, powerful left guard.

The current left guards on the roster — Ben Bartch, Spencer Burford — aren’t big or powerful enough to create much movement at the point of attack.

I expect the 49ers to draft Savaiinaea in Round 2 if he’s available. He’s not as tall as Banks, but he’s just as wide, plus he’s stronger, faster and generally more athletic than him.

I’m calling my shot now. Savaiinaea to the 49ers with the 43rd pick.