SANTA CLARA — It wasn’t much in practice, but Monday’s session was enough to get the 49ers excited about what lies ahead with running back Christian McCaffrey.

Left tackle Trent Williams felt energized by the presence of “two-three,” referring to last year’s best offensive player in terms of numbers. Quarterback Brock Purdy, during a casual conversation with a few reporters, broke into a wide smile as he described requesting a trade from the turbocharged McCaffrey.

With the media window being less than five minutes during warmups, there was no time for anything other than catching a glimpse of McCaffery in uniform after missing the first eight games of the season with Achilles tendinitis that resulted in his placement on injured reserve in Week 2.

“You could feel him, just being able to see him there,” rookie running back Isaac Guerendo said. “It’s a different type of feeling so I’m really excited for him.”

McCaffrey humorously avoided a reporter’s “hello,” calling it a “gateway” to a group interview that will take place later in the week. Coach Kyle Shanahan is not available until Wednesday.

Now comes the hardest part for Shanahan and the coaching staff: determining when to activate McCaffrey, then deciding how much he will play at first. The 49ers began a 21-day window Monday with McCaffrey’s first practice.

That could happen as early as Sunday when the 49ers visit the Tampa Bay Buccaneers. That’s what’s been touted in the national media, although general manager John Lynch hasn’t said it’s a certainty.

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

If McCaffrey calls, he will go straight into the starting lineup and into the end zone. The running back’s impatience with his condition necessitated putting him on injured reserve, and the following weeks included a trip to Germany for treatment.

Twice Shanahan said, “We have to protect Christian from himself.” » The first time was before McCaffrey was injured and the question was how to spell the running back more wisely to keep him fresh and healthy.

The second time was when he ended up on injured reserve, which immediately reduced the stress levels of everyone involved and prevented McCaffrey from approaching his rehab like he s This was a commando raid rather than a situation to be taken slowly, surely and seriously in the hope of achieving an outcome. him back for November and beyond.

Once upon a time, Shanahan was a firm believer in rotating running backs. He never had a 1,000-yard rusher with the 49ers in his first seven seasons. Only Carlos Hyde, in Shanahan’s first year in 2017, played more than 70% of the snaps.

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

Over 10 starts after his arrival, McCaffrey played 72.5% of all snaps and 77.4% in the postseason. Last season, he played a record 81% of all snaps in 16 starts, then 94.6% in tense playoff games against Green Bay, Detroit and Kansas City.

The only running back above 70% this year among NFL leaders is Philadelphia’s Saquon Barkley, at 75%. Jordan Mason, the 49ers’ leading rusher with 685 yards, is at 63%.

Coincidence or not, McCaffrey’s 2023 workload that earned him a two-year contract extension was followed by the diagnosis of Achilles tendonitis. McCaffrey’s father, Ed, told the Ross Tucker Podcast last month that the illness in both legs was the result of overtraining.

When McCaffrey speaks this week, don’t be surprised if it’s a reprise of his last interview from Sept. 12 with the 49ers preparing to take on the Minnesota Vikings. He had already missed the first game against the Jets and had no intention of missing another game.

“My mentality is I’m playing this week,” McCaffrey said. “That’s where I’m at. This is my mentality every week. I’m not lying. I think as soon as a player says, “Maybe I’ll play, maybe I won’t,” that’s not a good mentality to go into the week with when you’re a little bit on the fence . So for me, I’m ready to go.

He wasn’t, as it turned out, and it’s now up to Shanahan to have the final say on how much McCaffrey plays, with the end game being to keep him as healthy as possible for a surge. nine games for the playoffs that could include a wild card week.

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

“We would have never heard of Guerendo or seen the excellence of Mason if Christian was healthy,” Williams said. “There is a positive side to all of this. Now we know that without Elijah we still have a very deep backfield.

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

It is within Shanahan’s power, as a playmaker and designer, to lighten McCaffrey’s workload between the tackles while keeping him on the field as a potential receiver, either wide out, in the slot or moving.

That’s what Shanahan was trying to make in June, even though he expected competitive resistance from McCaffrey.

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

Being too greedy could end up with last year’s NFL Offensive Player of the Year back on the sidelines with the season on the line, and there’s unlikely to be time for another trip to Germany before the 49ers find out if they are a playoff team or not.