One of the more notable undrafted rookies the 49ers landed this year did not even last one week on the team's 90-man roster.

At the conclusion of the rookie minicamp, the 49ers unceremoniously parted ways with Baylor wide receiver KD Cannon. The 49ers filled his roster spot with the signing of unheralded Georgia Southern wide receiver B.J. Johnson, who was invited to attend the minicamp on a tryout basis. The New York Jets claimed Cannon off waivers.

While there were questions about the urgency with which Cannon performed during the practices, 49ers wide receivers coach Mike LaFleur said the Johnson-for-Cannon swap had more to do with the team being impressed with Johnson.

“Nothing happened with KD Cannon,” LaFleur said. “It had nothing do with KD. It was more of a testament to what B.J. showed.”

Cannon ranks No. 3 all-time in Baylor receptions (195), receiving yards (3,113) and touchdowns (27). But he was not one of the 32 wide receivers selected in the draft. The 49ers invested a fifth round draft pick in Louisiana Tech slot receiver Trent Taylor.

Cannon was waived after the 49ers’ rookie minicamp last month, while the 49ers kept undrafted rookie wide receivers Victor Bolden (Oregon State) and Kendrick Bourne (Eastern Washington).

Johnson’s best college season came as a senior when he caught 42 passes for 600 yards and three touchdowns. Johnson is 6 foot 1, 210 pounds, while Cannon is listed at 5-11, 182.

LaFleur said the 49ers liked the toughness he showed while fulfilling his blocking responsibilities in Georgia Southern’s run-based offense.

“When we brought him here, seeing that size, seeing his hands, we thought, ‘This is a guy we definitely want to work with,’” said LaFleur, who noted that Johnson has been spending time with veteran Pierre Garçon. “He’s done a really good job. He really loves it.”

Johnson concluded practice on Thursday with a sprawling intermediate reception in the middle of the field on a pass from fellow rookie quarterback C.J. Beathard. When Johnson realized nobody had touched him while he was on the ground, he got to his feet and finished off the 67-yard touchdown with linebacker Donavin Newsom and safety Malik Golden in pursuit. (The 49ers waived Golden on Friday.)

LaFleur said a premium is placed on how well a player separates and how he performs on plays in which the ball is not thrown his way. The 49ers' coaching staff is always watching, he said.

“There’s one ball out there every single time we snap the ball, but we’re watching every single thing you do,” LaFleur said. “We’re watching if you’re, first of all, on your details. Second, we’re watching if you don’t get the ball. Are you separating? When you don’t get the ball and someone else gets it, are you transitioning to go block for that guy?”