Michael Crabtree
The 49ers Number 1 receiver is back, and this time he will be here all season. It strange to think that this will be the 1st year that we will likely get solid production from him for an entire season, and he should produce well. He came on a lot stronger than everybody thought last season, and contributed to so many aspects of the 49ers passing game. Gaining 284 yards with an impressive 14 yards per reception, in only 5 games is pretty good. More importantly is that he takes away coverage from all of the 49ers other weapons, and will have more chemistry built with Kaepernick given he will be around for training camp. Furthermore, given his 85 reception, 1,100 yard season the year before, I think we can expect him to be a solid WR1 in most fantasy formats. I personally expect him to be the largest contributor on the 49ers offense this year, outside of Colin Kaepernick. A reasonable expectation is about 80 yards per game, with about 1,200 yards total, and 10 touchdowns.
Anquan Boldin
Q came on stronger than most people expected him too this year, and provide a necessary safety blanket at the beginning of the season for the 49ers. His ability to catch in traffic is 2nd to none given his strong hands, and exceptional route running. That being said, a dip is production is highly likely given how much more explosion this offense added in the offseason. Both Crabtree returning, and the addition of Stevie Johnson will likely cut into his production. Furthermore, even if the 49ers use more 3WR sets, they are unlikely to stray away from a running game that has depth for days. That being said Anquan should still be a decent fantasy option as a WR3, or a solid bench player. Given that he had 85 receptions for 1,179 yards, I think it would be fair to expect about 70 receptions for about 925-1,000 yards, and 7 touchdowns.
Stevie Johnson
Every 49ers fan is extremely excited for the Sherman breaker addition. Johnson took advantage of Richard Sherman in their last match up, going over 100 yards on 9 receptions. Now he has Kaepernick, a huge upgrade from Ryan Fitzpatrick, and a generally more talented team surrounding him. Still he will be fighting for targets during the season, and given his lack of production last year we shouldn't get too excited. If you are a superstitious person, you could play him against the Seahawks in hopes that he produces against the toughest secondary in the NFL. That aside, I think it is reasonable to expect about 600 yards on 40-50 receptions, with 3-4 touchdowns. Let us not forget that he still the 4th option after Crabtree, Boldin, and Davis. But his unique skill set will allow him to have big game here, and there.
Vernon Davis
Davis was a consistent fantasy producer with Kaepernick on the field last season, despite chemistry struggles the year before. As a player I had on my own team, he was very consistent, but had his games where he just disappeared. However, 13 touchdowns over the course of a season is some serious production from a TE, and he likely to produce similar number again given that he is the 49ers tallest option on offense at 6'3. He is also their fastest player on offense, and gives him unique opportunities to get the ball at times when other 49ers can't. He is still sharing a lot more targets this year, so I think 45 receptions for 800 yards, and 8 touchdowns is reasonable production for him this season.
Frank Gore
Frank the Tank is on his last legs as a runner at age 31, and let me be honest his production will likely slip quite a bit this season. I think a running-back by committee approach is something that 49er fans will be seeing sooner, rather than later. Furthermore, it was easy to see that he started to struggle immensely near the end of last season as he started to wear down. I probably wouldn't touch him in most fantasy leagues, and expect him to produce about 800 yards on 200 carries, with about 5-6 touchdowns.