As he ran off the field, he pooled coach Lane Kiffin and secondary coach Marvin Sanders together and told them he had a declaration to make.
"He's not gonna catch another pass the whole game," Robey told his coaches.
Sure enough, Williams didn't make another appearance on the stat sheet. He finished with 22 yards on two catches, the other five-yard catch coming just before the touchdown.
After the game, Kiffin said Robey led the way for what was another sneaky-good performance from USC's defense.
Two years ago, the Trojans were downright bad. Last year, they were good at times and bad at others.
Now, they're just good -- especially in the turnover department, forcing another four from the Huskies on Saturday.
And, perhaps most important, they weren't just good for three quarters, either. They held up all the way through the fourth, not allowing Washington any points in the final 20 minutes.
"For three years, that's been our issue: Fourth-quarter defense," Kiffin said. "I thought our guys really played well and closed the game out."
Defensive back Josh Shaw, who made his debut at cornerback Saturday and had an interception, said he heard his teammates discussing just how much improvement they've made over the past year. He didn't see any of it because he transferred from Florida in January, but he believes it.
"I wasn't here last year, but the talk is that this defense is much improved," Shaw said after the game. "We're looking pretty good."
Really, USC's defense has been more consistent than its offense, allowing no more than 22 points in a game when not counting garbage-time TDs from Syracuse and Utah.
Asked if he agreed with that assertion after Saturday's game, receiver Marqise Lee nodded his head.
"As of right now, you could say that," Lee said. "I'm not even gonna lie."
Shaw steps right in
Cornerback Torin Harris exited the game because of a head injury three minutes into the second quarter, but it didn't turn out to be a big issue.
Shaw replaced him and didn't miss a beat, recording five tackles and the interception. (He also had a fumble recovery on special teams.)
"I didn't come out after I came in," Shaw said afterward. "I know what I can do, my teammates know what I can do, and so do the coaches, so the trust was there. I know they didn't have any worries with me going in."
Kiffin said it "wasn't the plan" to have Shaw play so much so soon at corner. He just moved part-time to the position in practice this week when Harris struggled against Utah last week, but he was still considered primarily a safety.
Robey said Shaw proved he could be the guy at the troublesome second corner spot for the rest of the season, especially with the way he jumped right in.
"It just shows his willingness to be on the field and that he's always ready," Robey said. "Call his number any time. That guy's on it."
Starling a quiet star
The biggest play of the game was made by safety Jawanza Starling, who forced and recovered a fumble from Keith Price inside USC's five-yard line to reverse momentum and put USC in control in the fourth quarter.
Of course, it brought back memories to a similar recovery Starling made last October, against Notre Dame, when he scooped up a ball that quarterback Dayne Crist dropped at the same spot on the field and returned it the other way for a touchdown.
Starling, now a senior, said the circumstances were different this time, although he did think his play Saturday had a big impact on the game. USC brought him out for the postgame news conference and Kiffin praised the play and Starling's overall play, too. He's quietly performed nearly to the caliber of the two more highly-rated Trojans defensive backs, Robey and safety T.J. McDonald.
"Jawanza's really improved," Kiffin said. "He's really having a really good senior year."
Down 24-14 at the time, Washington was facing a second-and-goal from the USC three-yard line, so the Huskies appeared on the verge of making a one-score game. They never seriously threatened after Starling stepped in to strip Price near the line of scrimmage.
"We've come to expect that from him," center Khaled Holmes said of Starling. "He's a great player, and he's had a hell of a season."
No rain, but plenty of wind
All week, the talk was that there'd be a rainstorm in the Pacific Northwest just in time for the Trojans to take on the Huskies. USC even turned on its practice-field sprinklers Thursday to prepare for the possibility.
But it turned out that there wasn't any sort of precipitation during the game, and it wasn't even all that cold, either. There was one weather-related issue, though: It was windy, causing major problems on punt returns.
Robey muffed two of the five punts he fielded. USC recovered both, but even that was problematic.
"The wind was crazy," Robey said. "I guess the stadium's made a different way, but the ball was dancing in there tonight.
"I was just trying to get my hand on it and field it nicely."
"The wind caused the ball to go a little bit crazy," Lee said. "Going against it was tough."
USC has been terrible in the third quarters of games this season. In the six 15-minute periods they've played after halftime this year, the Trojans have been outscored 43-14.
In the other three periods, they've beaten teams by a combined score of 180-68. Kiffin had no answers when asked about it after Saturday's game but indicated he plans to work on a potential fix.
"That's a good question," Kiffin said. "I don't know. We have not come out and played very well in the third quarter. That falls on the coaches. We need to do a better job adjusting."
USC kicker Andre Heidari missed another field-goal attempt after missing two against Utah last week, but he thought he did "a lot better" in keeping his composure this time around.
Heidari got into it with some Utes fans in Salt Lake City last week. He was mostly silent Saturday.
He converted a 23-yard field goal in the first quarter with ease, then had a 41-yard attempt blocked in the third. He downplayed the miss and said he's still working his way back from surgery to repair a torn meniscus suffered in the season opener against Hawaii.
"My knee's feeling a little bit sore right now," he said. "It happens. I just came off surgery three weeks ago."
Asked when he would resume kickoffs -- walk-on Craig McMahon continues to handle them -- Heidari said it could be until "the end of the season or next season" before he felt fully healthy.
"I don't have a meniscus in my right knee anymore," Heidari said. "Try to play on a no-knee meniscus.
"It's kinda tough."
Final notes: USC has now gone a school-record 187 straight games without being shut out, breaking the previous record of 186 with Heidari's first-quarter field goal. The last time the Trojans were shut out was at Washington in 1997. ... Since John Baxter took over USC's special-teams unit in 2010, the Trojans have blocked a combined 17 punts, field-goal attempts and extra-point attempts. ... Tight end Randall Telfer, safety Demetrius Wright and cornerback Kevon Seymour all came on the trip to Seattle but did not suit up. Defensive end J.R. Tavai played for the first time since he suffered an injury against Syracuse in Week 2. ... Woods could break USC's all-time receptions record next week against Colorado. With five catches against Washington, he now sits just four short of Dwayne Jarrett's 216-reception record.