Summary: Receiver Michael Crabtree returned to the practice field for his most extensive work since being sidelined with a right calf strain early in practice. Crabtree caught a handful of passes during the 7-on-7 and team portions of practice. He did not participate in the two-minute drill.Meanwhile, rookie receiver A.J. Jenkins had his best day of camp. Jenkins had three receptions from Josh Johnson and a more impressive one from Scott Tolzien. Late in practice, Jenkins made one of the better catches of camp when he elevated in traffic to pull down a 25-yard dart from Tolzien, showing great body control in the air. Jenkins made the grab against the first-team defense. "Every day he's getting better," Crabtree said of Jenkins.Midway through practice, coach Jim Harbaugh raised the stakes for a two-minute drill. With post-practice sprints on the line, Alex Smith and the first-team offense marched down the field to get into the end zone.On fourth-and-goal from the six, Smith went through all his options before pulling it down, rushing right, and diving into the end zone to condemn the defense to extra conditioning.Tolzien made a number of nice deep passes. His touchdown to undrafted rookie receiver Brian Tyms was the offensive play of the day, and he dropped a pretty 30-yard pass over Ted Ginn's left shoulder down the right sideline later.Injury report: LaMichael James did not participate in practice, and his status is unknown. It was the first practice James has missed during training camp. Offensive lineman Jason Slowey sat out his third practice with an undisclosed injury. Receiver Joe Hastings (right leg), cornerback Curtis Holcomb also did not participate. Running back Jewel Hampton (foot) is on the non-football injury list, while outside linebacker Darius Fleming (knee) is on the physically-unable-to-perform list.Offensive play of the day: Tolzien showed an adept feel for the long ball. In the first 11-on-11 drill of the day, with the blitz coming, he hung in to hit Brian Tyms with a deep ball to the left side. Tyms elevated over starting cornerback Tarell Brown to haul in the touchdown. Anthony Dixon helped provide protection for Tolzien with a blitz pickup that drew raves from the coaching staff.Smith-Moss connection: It wasn't the play of the day, but in an 11-on-11 red-zone period, Smith felt pressure and stepped up in the pocket nicely before throwing to Randy Moss cutting across the back of the endzone for the touchdown. Smith and Moss haven't exactly torched the 49ers defense this training camp, so it was positive to see them connecting -- and looking in sync -- in the red zone.Defensive play of the day: Donte Whitner and Carlos Rogers each pulled down interceptions. Whitner's was more impressive, as he jumped an inside rout and collapsed on Johnson's low pass. Rogers' pick was deflected into the air before he corralled it in the middle of the field.Eye on reps: The bulk of the quarterback snaps went to third- and fourth-string QBs Johnson and Tolzien. Johnson had an up-and-down day of work with several of his passes sailing high of the mark. Tolzien was sharper, especially looking downfield.Getting physical: In a 1-on-1 individual blitz pick-up drill, Dixon locked up Ahmad Brooks and threw him backwards. A play later, Aldon Smith looked to get around starting fullback Bruce Miller. When Dixon and Brooks squared off again, there was a little something extra behind the initial contact. It was a good drill for Dixon, who turned away a NaVorro Bowman spin move as well.Notable: In the special teams period of practice, the ball ended up in Brooks' arms on the kick return. It won't be a plan of attack for the 49ers, who have Ted Ginn, Kendall Hunter and James listed on the depth chart for kickoff returns, but you never know where a squib kick will end up.Next practice: The 49ers return to practice on Wednesday from 5 to 8 p.m. None of the 49ers' practices in Santa Clara this summer are open to the general public due to the ongoing stadium construction.