Ross didn't exactly call his shot the previous day, but he did tell those listening that his record-setting sprint was possible.
"Under 4.3 [seconds]," the former Washington wide receiver told reporters. "That's what I plan to run."
Buzz about Ross' run started after unofficial results had him breaking Johnson's previous record, set in 2008, with the first of his two scheduled 40-yard dashes. The NFL confirmed Ross' official time of 4.22 seconds later Saturday.
"When I got there, everything kind of got quiet. I had so much adrenaline," Ross told ESPN's Josina Anderson. "I was nervous right before I went, so I was up on my hands. Everything got quiet; I couldn't hear anything. And I just took off. I held my breath ... and it just went on from there."
Ross confirmed to Anderson on Friday that he will undergo shoulder surgery on March 14. He also missed the 2015 season at Washington after suffering a torn ACL during a spring practice earlier that year.
"I'm just thankful beyond measure, blessed, and just really happy to be in this situation," Ross told the NFL Network on Saturday. "Because two years ago, I was sitting on the couch for the whole season, torn ACL, and now to be in this position, I'm really thankful."
Ross elected not to run a second time, saying that he "cramped up toward the end" of his first run.
"[I'm] just real tight right now -- both calves, maybe dehydration," he said.
The timing devices at the combine use a handheld device to start the clock and an electronic eye at the finish. The clock is started when the prospect raises his hand that is touching the ground in a three-point stance at the start.
Ohio State's Curtis Samuel was unofficially clocked at 4.31 seconds in his 40 and was the second-fastest player among the wide receivers who ran inside Lucas Oil Stadium on Saturday.
Ross, who had 81 receptions for 1,150 yards to go with 17 touchdowns this past season, did not win an island for his trouble since he was wearing Nike shoes for his run.
Adidas had offered an island to any prospect who broke Johnson's record while wearing the company's 2017 Adizero 5-Star 40 cleats and then agreed to endorse the company's shoes for the entire 2017-18 season.
Adidas' offer included the caveat that an island would be awarded "as soon as reasonably possible" or that the company could pay the prospect $1 million instead.
"I really can't swim that well," Ross said. "And I don't have a boat, so, you know, I had to run in Nikes."
Nike signed Ross shortly after his record sprint, according to ESPN's Darren Rovell.