It was a quick appearance for redshirt freshman Mason Murphy on Saturday, but when reinforced by Lincoln Riley's comments Tuesday after practice, it could be viewed as a significant one.

With starting left tackle Bobby Haskins forced to the sideline by an apparent shoulder injury late in the first half of USC's 30-14 win over Washington State, it was Murphy and not redshirt sophomore Courtland Ford who took over at left tackle for four plays.

Ford, who opened the season taking the first reps of an even timeshare with Haskins at left tackle, did not play at all in the game.

"Just felt like it was the right decision," Riley said. "We've got some guys that have been practicing well, we've got some tough decisions to make there. We felt like in that situation it was the right time to give Mason a shot."

It's hard to know if that signals a formal change on the depth chart, with Ford going from co-starter to third team, but it's something to monitor.

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Murphy had previously played 16 snaps in the season opener and then 6 snaps in Week 3 when Ford was sidelined by injury and Haskins had to come out of that game briefly.

Ford missed two games recovering from his unspecified ankle/foot injury and played only 15 snaps in the win over Arizona State, all in the first half. He struggled during that game, giving up 2 pressures in his 8 pass-blocking snaps and was called for a costly holding penalty that wiped out a long touchdown pass to a wide-open Mario Williams.

Riley said last week that he stuck with Haskins the rest of that game because he and the offense were both playing well. Haskins, the redshirt senior transfer from Virginia, had turned in his two best performances against Oregon State and Arizona State, allowing just 1 pressure combined between the two games. He allowed 3 pressures, per PFF, on Saturday vs. Washington State and drew a penalty.

However, there seems to be no question now as to his hold on the starting role -- the question is whether Murphy has truly usurped the veteran Ford for the No. 2 left tackle job.