Shanahan was asked how his young wideouts did on Saturday night against the Kansas City Chiefs.
"Some, I think, did better, some did worse," Shanahan said. "Overall, I thought we did alright. I'm always pretty hard on the receivers, though. I still think we need to keep doing better than we have been, though."
The 49ers' second-year receiver, Dante Pettis, has had an uneven offseason. Once considered to be a potential breakout player for San Francisco this season, Pettis' work on Saturday night continued into the fourth quarter. Shanahan was asked why he left the receiver in that long.
"Just because I believe he needed to be," he answered. "He's still trying to earn a role on this team, and he's still trying to show us what he's capable of doing, consistently."
Despite playing in all three games, Pettis hauled in his first catches of the preseason on Saturday, ending the night with three catches for 36 yards and a fumble.
Shanahan also discussed third-year wideout Kendrick Bourne, who had two catches for 25 yards against the Chiefs, increasing his preseason total to five catches for 66 yards with a touchdown.
"Bourne's a good receiver," Shanahan said. "He's a big body, who plays big. He's fearless out there. He's not scared to get hit. He blocks as well as any of the receivers we have on our team, but him, like a few other guys, he just needs to be more consistent.
"I know he had the penalty, which wasn't a good one because we had a pretty good look with the play we were going (with), but he just has to be more consistent for us. He's done some things that have helped us a ton, but we need him to keep taking a step forward and making sure he only makes those good plays for us."