It was the first time Smith (offseason shoulder surgery) and Williams (broken leg) practiced all of training camp. McDonald (offseason bicep surgery) was nursing a minor leg injury for the past several days. The 49ers have been cautious with Smith and McDonald, and it's doubtful either will play a lot during the rest of the preseason.
Williams was taken off the PUP list Tuesday. Williams said earlier Wednesday that his return to the field is still a process, but he participated fully later in the practice.
The reinforcements are needed. The 49ers finished Thursday's preseason opener at Baltimore with four healthy defensive linemen.