In what’s become the most positive development from the first week of 49ers training camp, Arik Armstead continued his impressive showing Thursday.

The defensive lineman is catching the attention of his teammates.

“Have y’all been watching the kid?” safety Eric Reid said. “He’s killing it. He’s focused. He’s making plays. When you see him, he’s doing what you think he should do based on the way he looks. The kid’s a monster.

“If (Armstead) could bring DeFo (DeForest Buckner) along with him. That would be awesome, too.”

Armstead has been the most impressive player on San Francisco’s defense in the early going. Something has clicked with the former first-round pick, and he appears to be realizing he can be tough to contain given his immense physical gifts.

With the starting defense, Armstead has worked at right defensive end opposite Buckner, the recent seventh-overall pick, who played on the left side. Buckner’s been no slouch in practice either.

Toward the end of Thursday’s session in full-team drills, Buckner had one ‘sack’ of Blaine Gabbert and created pressure that led to a sack for Ahmad Brooks two plays later. He also ruined a screen play by covering the running back and making the tackle behind the line of scrimmage.