At the halfway mark of the preseason, teams are getting a pretty good grasp on the potential of their first-year players. Two games worth of film provide coaches with a decent sample size to evaluate how their rookies fare during live action.

Pro Football Focus has taken note of three San Francisco 49ers rookies who have turned heads so far. Here's a look at what PFF had to say regarding some of the 49ers promising young talent.

Dante Pettis

The 49ers second-round pick had a standout training camp. Pettis has flashed with his speed and his ability to get open in coverage. He broke free and nearly caught a 63-yard touchdown on an overthrown pass by C.J. Beathard against the Houston Texans last Saturday. He has amassed 85 yards over the first two preseason games, headlined by a 53-yard reception against the Dallas Cowboys.. PFF recognized Pettis as one of the under-the-radar rookies to watch out of the NFC West.

"Pettis is already making a name for himself among coaches and players in his first 49ers training camp. The former Washington wide receiver is a smooth route-runner with reliable hands that has the ability to develop into a security blanket for quarterback Jimmy Garoppolo.

"Pettis has the good fortune to develop behind veteran Pierre Garçon who finished tied for first in the NFL in drop rate with zero drops on 40 catchable targets before an injury ended his season. If Pettis can continue his positive momentum this preseason, he should be able to carve out a role in multi-receiver sets in San Francisco this season."

D.J. Reed Jr.

Reed is another rookie who has impressed in camp. The 49ers defensive back has taken on the challenge of learning both nickel corner and free safety while acclimating to the speed of the NFL. PFF revealed Reed at No. 7 on the top 10 rookie performances of the preseason.

"Reed is technically listed as a safety on the 49ers depth chart, but through two games he's taken 57 of his 75 snaps lined up as a slot cornerback. He's been targeted six times there and while he's allowed four catches, only one has gone for a first down while three have resulted in stops."

Mike McGlinchey

The 49ers first-round pick immediately stepped into the starting right tackle job. Thus far, McGlinchey has held his own against some of the NFL's elite in Dallas Cowboys' DeMarcus Lawrence and All-Pro lineman J.J. Watt during the team's joint practices with the Houston Texans. PFF has McGlinchey (64.1) graded higher than his fellow offensive linemen taken in the first round: Quenton Nelson (62.1), Kolton Miller (53.2), Billy Price (56.4) and Isaiah Wynn (44.5).

"The 49ers new right tackle has played 44 of his team's 143 offensive snaps so far this preseason and has graded out much better as a pass-protector (69.0 pass-blocking grade) than as a run-blocker (58.8 run-blocking grade). In two games, McGlinchey hasn't allowed a single pressure on any of his 26 pass-blocking snaps."