What he misses most of all is being a contributing player in the NFL.
Over the past several days, Jacobs has posted pictures of himself while with the Giants -- much to the objection of some 49ers fans who follow him on Instagram. Jacobs, an eighth-year pro, played on two Super Bowl-winning teams with the Giants.
Jacobs originally said he had not posted any photos while with the 49ers simply because he has not been in the picture since signing.
“I am on this team rotting away so why would I wanna put any pics up of anything that say niners." Jacobs wrote on Instagram in response to a fan. "This is by far the worst year I ever had, I’ll tell you like I told plenty others.”
Jacobs has since added several photos of himself with the 49ers.
On Saturday, Jacobs explained himself via his Twitter account:
"I don't understand why people are angry at me because I wanna do what I am paid to do, I am a competitive person, I think people should be mad if I didn't wanna play, but I forgot the people that's pissed they don't have a athletic bone and their body. As for all of my Instagram photos I don't have any niner pics, if you'll find me some pics I'll put them up."
I spoke with Jacobs on Friday, and he reiterated his frustration with being an absolute non-factor in his first (and, safe to say, only) season with the 49ers.
Jacobs is getting paid a lot of money to do nothing.
The 49ers awarded Jacobs a $150,000 signing bonus after the Giants cut him. He gets paid $55,000 per game ($950,000 base salary) whether he suits up or not. And he gets paid another $12,500 in per-game roster bonuses when he suits up. Thus far, he has suited up for just three of the 49ers' first 12 games.
He carried four times for 6 yards last week in the 49ers' 16-13 overtime loss to the St. Louis Rams. He picked up 3 yards on a third-and-1 play in the first quarter. The 49ers scored their only offensive touchdown on that drive.
There are no guarantees Jacobs will have much of a role on Sunday against the Miami Dolphins, either.
The 49ers are expected to activate rookie running back LaMichael James, a second-round draft choice, for the first time this season. It's not known whether Jacobs will also be in uniform. Starting running back Frank Gore and Anthony Dixon, who has a key role on special teams, have been active for every game.
The 49ers are in the process of trying to figure out how to split up the carries after the season-ending injury backup running back Kendall Hunter.
"That's part of the game plan," 49ers coach Jim Harbaugh said "That's part of the scheme. We have some other backs that we feel confident in as well. But Frank is one of the best, if not the best back in the league. So he's going to run and he's feeling good. He had a good week at practice."
Last week, Gore carried a season-high 23 times for just 58 yards and a touchdown in the 49ers' loss. Offensive coordinator Greg Roman said on Thursday that Gore was overworked.
"Whatever back we have in there to complement Frank we feel good about," Roman said. "It's definitely something we don't want to overload Frank with over the length of a long season.
"(I) really believe we gave him a few too many plays last week. Whatever back we put in there, we feel really good about and anybody that's on the active roster could possibly play. LaMichael's a guy that's been working hard and it's very possible he could be playing this week."
And if James is active, it might be another week in which Jacobs is out of the picture.