San Francisco 49ers running back Christian McCaffrey's availability for the upcoming game against the Minnesota Vikings remains uncertain as he continues to recover from calf and Achilles injuries. Niners coach Kyle Shanahan stated in a conference call that McCaffrey would be evaluated on a day-to-day basis throughout the week.

Shanahan emphasized that the Achilles injury is causing more concern than the calf, explaining that Achilles tendonitis can fluctuate in intensity. It is a condition that requires careful management to prevent further complications.

To the surprise of many, McCaffrey was inactive for the season opener against the New York Jets after expressing optimism about his readiness to play earlier in the week. Third-year veteran Jordan Mason stepped in as the starting running back and impressed, accumulating 147 rushing yards and a touchdown on 28 carries.

Mason revealed in an on-field interview with ESPN's Lisa Salters that he found out he would be starting only on Friday night before the game. Shanahan clarified that the decision was made on Monday when McCaffrey arrived at Levi's Stadium, expressing discomfort with his injury. The coach also mentioned that the news might have been communicated to Mason earlier in the week to boost his confidence.

Teammates, including receiver Deebo Samuel Sr. and fullback Kyle Juszczyk, admitted they were also uncertain about Mason starting until Monday. However, they expressed faith in Mason's abilities and were confident that he would excel in the role.

McCaffrey's calf and Achilles injuries began bothering him around August 6, causing him to miss the preseason as initially predicted by Shanahan. The calf injury is reminiscent of a similar one McCaffrey sustained during a Week 17 victory against the Washington Commanders last year. He subsequently missed a nonessential Week 18 game against the Los Angeles Rams and returned for the NFC divisional round against the Green Bay Packers after a bye week.

Shanahan acknowledged that although McCaffrey is diligent about his recovery, the decision to sit him out was influenced by the early stage of the season and the lower extremity injuries. The coach mentioned that McCaffrey believed he could play if it were a playoff game but agreed that prioritizing his long-term well-being made the choice straightforward.

As for McCaffrey's potential participation against the Vikings, the decision is likely to be made closer to game time. Additionally, the team must consider playing on artificial surfaces in their upcoming matchups against the Vikings and the Los Angeles Rams, adding another factor to evaluate McCaffrey's readiness.

In other injury updates, safety Talanoa Hufanga, who is recovering from a torn ACL suffered in November last year, has a chance of returning against the Vikings. Receiver Jauan Jennings and guard Aaron Banks will also be monitored on a day-to-day basis due to ankle and calf injuries, respectively.

The 49ers' coaching staff and medical team will closely assess the players' conditions and make the necessary decisions based on their recovery progress and overall readiness for Sunday's game.