SANTA CLARA – Not much happened in practice, but Monday’s session was enough to get the 49ers excited about what’s to come with running back Christian McCaffrey.

Left tackle Trent Williams felt energized in the presence of the “two-three,” a reference to last year’s top offensive player in scoring. Quarterback Brock Purdy smiled broadly as he described switching to the turbocharged McCaffrey in an informal conversation with several reporters.

With the media window during warmups being less than five minutes, McCaffery, who missed the first eight games of the season with Achilles tendinitis and was placed on injured reserve in Week 2, had no time for anything other than a moment in the jersey.

“You could feel it because you could see him there,” rookie running back Isaac Guerendo said. “It’s a different feeling so I’m really excited for it.”

McCaffrey humorously sidestepped a reporter’s “hello,” calling it a “gateway” to a group interview later in the week. Coach Kyle Shanahan isn’t available until Wednesday.

Now comes the toughest part for Shanahan and his coaching staff; Determining when McCaffrey will step up and then deciding how much time he will play initially. The 49ers began a 21-day pause with McCaffrey’s first practice on Monday.

That could happen on Sunday when the 49ers visit the Tampa Bay Buccaneers. It was framed that way in national media reports, but chief executive John Lynch refrained from declaring it definitively.

“Does that mean playing against Tampa? No,” Lynch said in a recent “Game Plan” interview with 49ers-produced play-by-play announcer Greg Papa. “We’ll see where this goes.”

If McCaffrey is making the decision, his destination will be straight into the starting lineup and the end zone. His impatience with the running back’s condition necessitated placing him on injured reserve, and the following weeks included a trip to Germany for treatment.

Shanahan said twice: “We have to protect Christian from himself.” The first was before McCaffrey’s injury, and the question was about drafting the running back smarter to keep him fresh and healthy.

The second time was when he was placed on injured reserve, which immediately reduced the stress levels of everyone involved and prevented McCaffrey from approaching his rehabilitation as if it were a commando raid rather than a situation that needed to be handled slowly, surely, and seriously in the hope of a recovery. He’s back for November and beyond.

Shanahan used to be a big believer in returning runs. He never had a 1,000-yard rusher in his first seven seasons with the 49ers. Only Carlos Hyde played more than 70% of snaps in Shanahan’s first year in 2017.

The highest percentage since then was Elijah Mitchell, who received 64% of snaps in 2021. Then, on October 20, 2022, McCaffrey arrived from Carolina for four draft picks. McCaffrey instantly became Shanahan’s favorite toy.

McCaffrey played 72.5% of all snaps and 77.4% of the playoffs in 10-plus starts following his arrival. He shot a league-high 81% in 16 starts last season and then shot 94.6% in tough playoff games against Green Bay, Detroit and Kansas City.

The only player among the NFL’s rushing leaders this year to drop over 70% was Philadelphia’s Saquon Barkley at 75%. Jordan Mason, the 49ers’ leading rusher with 685 yards, is at 63%.

Coincidence or not, McCaffrey was diagnosed with Achilles tendinitis after his workload in 2023 earned him a two-year contract extension. McCaffrey’s father, Ed, told the Ross Tucker Podcast last month that the condition in both legs was the result of overtraining.

When McCaffrey speaks this week, don’t be surprised if it’s a repeat of his last interview on Sept. 12, when the 49ers were preparing to face the Minnesota Vikings. He had already missed the first game against the Jets and wasn’t planning on missing another game.

“My feeling is to play this week,” McCaffrey said. “I’m there too. That’s my mentality every week. I can’t tell lies. I think if a player says, ‘Maybe I’ll play, maybe I won’t,’ that’s not a good mindset to go into a week where we’re indecisive. So for me, I’m ready to go.”

Apparently it wasn’t, and now it’s up to Shanahan to have the final say on how much time McCaffrey plays; The postseason will keep him as healthy as possible for a nine-game stretch into the postseason. A wild card week.

The good news is that with Mason, rookie Isaac Guerendo and Purdy’s flashy footwork, the 49ers are averaging 159.0 yards per game (fourth in the NFL) and 5.1 yards per carry. The 49ers averaged 140.5 yards and 4.8 per carry last season.

“If Christian had been healthy, we would never have heard of Guerendo or seen the greatness of Mason,” Williams said. “Some of them also have a good side. “Now we know we have a very deep backfield even without Elijah.”

Ideally, McCaffrey would help the 49ers improve their 48% touchdown rate in the red zone.

As a quarterback and designer, it’s within Shanahan’s power to lighten McCaffrey’s workload between the tackles while also keeping him on the field, wideout, in range or on the move as a potential receiver.

That’s the point Shanahan was trying to make in June, although he expected some challenger resistance from McCaffrey.

“You want to take some of that away from him and give it to the other guys,” Shanahan said.

Too much greed could see last year’s NFL Offensive Player of the Year sidelined again with the season in the balance, and the 49ers are unlikely to find time for another trip to Germany before they discover whether they’re a playoff team or a playoff team . Negative.