- Earned playing time in 2024: Isaac Guerendo took advantage of opportunities with the San Francisco 49ers last year, stepping up due to injuries and showing promise with a 5.0 yards per carry average.
- Backup with upside in 2025: While primarily behind Christian McCaffrey, Guerendo holds value as a potential fantasy starter should McCaffrey suffer another injury.
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Estimated Reading Time: 5 minutes
PFF’s Fantasy Football Player Profile series delivers the most in-depth fantasy football analysis available for the 2025 season.
Using PFF’s exclusive data, we evaluate player performance, competition for touches and how teammates and coaching staffs
Last updated: 7:15 a.m. Tuesday, June 17
Player performance
Isaac Guerendo was the fourth-round pick by the San Francisco 49ers in the 2024 NFL Draft. The 49ers had invested a lot of draft capital in running backs in recent seasons – Trey Sermon and Elijah Mitchell in 2021, Tyrion Davis-Price in 2022 and the trade for Christian McCaffrey in 2022. Guerendo didn’t have a clear path to playing time as a rookie, as McCaffrey, Jordan Mason and Mitchell were all potentially ahead of him on the depth chart.
Mitchell suffered a hamstring injury in training camp, which landed him on season-ending injured reserve. McCaffrey had Achilles tendinitis, which cost him the first half of the season. This left Mason at the top of the depth chart and allowed Guerendo to be the top backup immediately. Guerendo played 50 snaps over the first seven weeks compared to Mason's 328. He ran 10 times for 99 yards in Week 6 while Mason dealt with his own injury. Mason also missed most of Week 8, where Guerendo ran 14 times for 85 yards and a touchdown.
McCaffrey was back for Weeks 10-13, and Guerendo only played five snaps and earned one carry in the first three games. He ran four times in a blowout loss in Week 13, when both McCaffrey and Mason suffered season-ending injuries. Guerendo was the clear starter in Weeks 14 and 15, finishing with 15 carries for 78 yards and two touchdowns followed by 16 carries for 57 yards. However, Guerendo suffered a hamstring injury, causing him to miss Week 16. While he played over 60% of San Francisco's snaps in Week 17, he ran nine times for 34 yards and caught four passes for 65 yards, making it the best game of his season as a receiver. The 49ers largely rested players in Week 18.
Guerendo averaged 5.0 yards per carry, seventh among running backs with at least 75 carries, but he didn’t grade as well as most running backs typically who have earned that many yards per carry. Part of that is receiving a lot of help from his line, averaging 2.0 yards before contact per carry, tied for fifth, while his 3.0 yards after contact per carry was only 24th-most. He benefited with 18% of his total rushing yards coming from a single 76-yard run, but he gained a first down and avoided tackles at a below-average rate.
He was used sparingly on passing downs. He managed a solid 1.42 yards per route run on a low target rate, but had a fumble and dropped a pass compared to just 15 receptions, leading to a low receiving grade.
Projected role
The 49ers generally used Jordan Mason or Guerendo as two-down backs when they were the starters, but they did not play much on third downs. When Guerendo was used as a backup, he played more at the goal line and in short-yardage situations, as he’s 6 feet and 220 pounds.
He will likely fill that role with McCaffrey as the starter, and Guerendo getting some short-yardage chances to give McCaffrey a break. The 49ers moved on from Mason and Mitchell, which means Guerendo is the likely second player on the depth chart. The 49ers continued their run of drafting running backs, adding Jordan James in the fifth round. While James is smaller than Guerendo and unlikely to take the goal-line snaps away from him, there is at least a chance James can win the backup job from Guerendo.
If McCaffrey suffers an injury, we can expect Guerendo to have a similar role to his starts from last season, playing 60-75% of the 49ers' offensive snaps, being limited on third downs and running around 15 times per game. The only way Guerendo will have any fantasy value this season is if McCaffrey suffers an injury. All reports out now are suggesting McCaffrey is fully healthy, but he only played three games in 2020, seven games in 2021 and four games in 2024. The odds of Guerendo seeing some starts this season are likely higher than those of other backups.
Impact of teammates
Guerendo will play under Kyle Shanahan, who has historically run a run-first offense. They’ve passed more recently due to having Christian McCaffrey and Brock Purdy. However, the Deebo Samuel loss, along with Brandon Aiyuk returning from injury, could lead them to return to their run-heavy ways. Shanahan also has a history of having one clear early down back rather than a committee, which is why Guerendo won’t see much playing time unless McCaffrey is injured. In this case, he should see a lot of touches, assuming he beats out James.
The 49ers' offensive line wasn’t as elite as some past years, but it still had the third-highest overall grade. Left tackle Trent Williams saw his run-blocking grade drop from the 90.0s to 81.4, which is still very good but no longer as elite as it once was. He will be 37 years old by the start of the season, so we can’t expect him to return to his 2023 form. Finding Dominick Puni was a big win for the 49ers' offense. The primary concern heading into 2025 is at left guard after Aaron Banks landed with the Green Bay Packers. Nick Zakelj is penciled in for the starting role, but he hasn’t looked great in his two career starts.
This should still be one of the better offensive lines in the league, but it may fall out of the top five. They will be an asset to Guerendo whenever he touches the ball. Guerendo averaged 10.2 yards per carry on perfectly blocked runs and 2.9 yards on non-perfectly blocked runs. While those numbers are influenced by small sample sizes and will regress to the mean on more plays, it seems like the offensive line playing well is very important for Guerendo.
Bottom line
Guerendo is a solid handcuff option. He won’t have any fantasy value without an injury to Christian McCaffrey. Still, given McCaffrey’s injury history, there is a good chance Guerendo will be a fantasy starter for at least a few weeks this season.
Footnotes
- Statistics in tables and charts were chosen based on their ability to predict future fantasy performance on a per-game or per-opportunity basis or to describe the player relative to others at the same position.
- “Opportunities” are defined as passing dropbacks, rushing attempts and routes run as a receiver.
- Numbers are provided either by season or based on the past three years. For rookies, only college statistics are included. For non-rookies, only NFL statistics are considered, regardless of whether they played in college within the previous three years.
- As college competition is easier than NFL competition, most rookies are likely to see a decline from their historical numbers.
- Only FBS data is considered for college players and comparisons.
- Kneel-downs are removed from rushing data to provide cleaner quarterback rushing rate statistics.
- The table colors in this article range from blue (indicating good/high) to red (indicating bad/low).
- All percentiles and color codings compare the given player to others with a high sample of opportunities. Generally, the cutoff is one-third of the possible opportunities in the sample. If a player does not meet the threshold, they are still included in the comparison, though their results may appear better or worse than expected due to the smaller, less predictive sample size.
- Information on utilization classifications and their importance can be found here for running backs, wide receivers and tight ends.
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