Justin Blackmon has been on a tear ever since he returned from a four-game suspension to start 2013.
The Jacksonville Jaguars second-year wide receiver has caught 25 passes for 384 receiving yards with one touchdown in three games.
"They've made a lot of improvements here in the last few weeks," 49ers defensive coordinator Vic Fangio said on Thursday. "The evidence is on the tape when you watch it. And then the evidence is on paper when you look at their stats."
Fangio sees Jacksonville's play-making wideout having a big say in the team's increased yardage.
"Part of that's coincided with the return of Blackmon, too," San Francisco's coordinator said.
"And the quarterback is doing a pretty good."
Chad Henne has posted back-to-back 300-yard passing games while stepping in for second-year quarterback Blaine Gabbert. Henne, the veteran, will start Sunday against the 49ers at Wembley Stadium. Gabbert, now healthy from a hamstring injury, has been benched.
Henne found a way to spark the Jaguars by getting the ball to Blackmon and the team's other top wideout, Cecil Shorts III.
"They've changed it up quite a bit from the first couple of weeks," 49ers defensive tackle Justin Smith said of Jacksonville's offensive schemes.
Smith noted that Henne has been throwing the ball faster to minimize pressure on Jacksonville's struggling offensive line, a group that has allowed a league-high 28 sacks.
With more of a focus on shorter routes, Blackmon has become an integral part of Jacksonville's offense. The 6-foot-1, 210-pound wideout has been targeted 38 times in three games and has accounted for 30 percent of the Jaguars first downs during that stretch.
Blackmon has averaged 128 yards per game.
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He'll be challenged this week against San Francisco's No. 6 ranked pass defense.
The 49ers have only allowed three, 100-yard receivers all season. Green Bay wideout's Jordy Nelson and Randall Cobb, plus Arizona wide receiver Larry Fitzgerald all enjoyed success against San Francisco's defensive backs. Other than that, the San Francisco has clamped down on opponent's passing attacks.
Blackmon's emergence will be one of many key storylines in Sunday's NFL International Series matchup between the 49ers and Jaguars.
"They're a much improved offense right now when you compare them to earlier in the season," Fangio said.