STANFORD, Calif. (AP) -- Stanford's offensive line was in the middle of a meeting during spring practices earlier this year when a few large visitors walked into the room.
Current NFL linemen Jonathan Martin and David Yankey and former team captain Sam Schwartzstein popped in with a couple of other past players to give a surprise history lesson. They educated the new crop of Cardinal linemen about the responsibility they were inheriting and issued them a challenge.
''They told us they laid so much ground work for us, but we had the opportunity to take that to the next step, to keep progressing, to keep it moving forward,'' redshirt sophomore center Graham Shuler said.
While most offensive lines toil in anonymity, Stanford's has gained national attention during the program's recent run of success, which includes winning the past two Pac-12 titles. The unit, dubbed the Tunnel Workers Union, has been the bulldozer in front of a power running game and the anchor behind a pro-style passing attack.
With four new starters next to one of the country's top left tackles in Andrus Peat, the unit is in the early stages of another reconstruction. The new-look line will face its first major test Saturday when the 13th-ranked Cardinal (1-0) host Leonard Williams and No. 14 Southern California (1-0) in a much-anticipated Pac-12 tilt.
''The challenge this week is prominent,'' said Stanford coach David Shaw, who has remained steadfast in his belief that the offensive line will continue to meet its high standard this season.
Shaw said on Signing Day in February 2012 that his five current starters - Peat, left guard Joshua Garnett, Shuler, right guard Johnny Caspers and right tackle Kyle Murphy - had the potential to ''be one of the best offensive line classes in modern football history.'' He has stuck by that statement since, saying during training camp that the O-line could be as good or better than any he had during his first three years as coach.
But the group had its share of struggles in the opener, including a false start, holding and clipping penalties in the first half of a 45-0 rout of an overmatched UC Davis team. Kevin Hogan also was sacked once.
''Nowhere near our best,'' Peat said.
Peat and his fellow offensive linemen attribute most of the problems to communication. It's an issue that will need to be worked out fast with Williams and the Trojans' athletic defense visiting The Farm.
Williams, one of the nation's best defensive ends, controlled the line of scrimmage and had an interception in USC's 52-13 win over Fresno State. Shaw said he is one of the rare players whom Stanford will form its game plan around.
''We'll know where he is on every play and plan accordingly,'' Shaw said.
The other issue for Stanford's line is that it struggled to create those ''tunnels'' against UC Davis in the running game, which is the Cardinal's calling card on offense. Barry Sanders (43 yards on seven carries) and Kelsey Young (37 yards on seven carries) helped Stanford finish with 149 yards rushing, but the offensive line didn't produce big gaps and impose its will the way it usually does.
''The bar is set really high,'' Shuler said. ''The attitude in our offensive line room was a tad bit frustrated, but we were way more interested in moving forward and how we can fix it and what we can do to adjust to be as efficient as possible this week.''
Hogan said the offensive line is among the most tight-knit groups on the team and the linemen take it especially hard when they don't play well. He said watching how the group has performed against Stanford's defensive front seven in offseason practices gives him confidence they will show against USC just how good they can be.
''They play with a chip on their shoulder,'' Hogan said. ''They know that we lost all those great guys on the offensive line the past couple years. They want to prove that they're that next elite group, which I think they are. It helps motivate them.''
NOTES: Shaw said DE Aziz Shittu is expected to play against USC after sitting out the season opener with a toe injury. ... Backup LBs Joe Hemschoot and Kevin Palma will sit out Saturday's game with unspecified injuries. Shaw said he expects both to return at Washington on Sept. 27.
Antonio Gonzalez can be reached at: www.twitter.com/agonzalezAP