IRVINE, Calif. -- Cooper Kupp, the Los Angeles Rams' rookie slot receiver, made friends with the janitors at Eastern Washington University.

They were his lifeblood.

Kupp needed them to open the facilities in February so he could catch tennis balls from a machine two months before anyone was even thinking about football. He needed them on Saturdays, hours after the games that concluded long weeks, so he could pore over film deep into the night. Beau Baldwin, the former Eastern Washington head coach who is now the offensive coordinator at Cal, would often return to the office to pick something up and see Kupp sitting there, alone. Sometimes he would be watching practice film of an offensive lineman, repeatedly rewinding it because he wanted to know what everyone was doing on every play.

Baldwin coached college football players in the state of Washington for 22 years and never met a player with Kupp's work ethic.

"He didn't waste a minute, ever," Baldwin said. "I know a lot of people say it, but he truly wasn't going to let anyone outwork him."

Kupp left Eastern Washington with 6,464 receiving yards, more than any college receiver at any level. He set Football Championship Subdivision records for receptions (428) and receiving touchdowns (73), and he caught at least two passes in each of the 52 games he played. The Rams made him a third-round pick in this year's draft and are expected to use him as their No. 3 receiver, behind Tavon Austin and Robert Woods. By the end of the season, Kupp could lead the team in receptions.

On Wednesday, the day rookies reported for training camp at UC Irvine, he recalled where he was in his life nearly six years ago -- walking off the field after his final high school game without a single college offer in hand.

Kupp wanted to go to Yale, an Ivy League school he had the grades for. He thought he had impressed the Bulldogs.

"The coach that was recruiting me, his dad was actually at [a] game," Kupp said. "So I felt like, 'OK, this is going to be a thing for me. I have a good shot of going here.' That week, after that first game, the coach called me and said that they were going a different direction with it. So, right in the middle of the season, I lost the only interest that I had."

Kupp was a late bloomer who never possessed eye-popping straight-line speed. He comes from two generations of NFL players -- his father, Craig, played one season at quarterback and his grandfather Jake enjoyed 12 years as an offensive lineman -- but Kupp wasn't even deemed good enough to play in college. He sent tapes to a laundry list of coaches, publicized himself through a recruiting service and even had his grandfather work his connections at Washington, his alma mater. Nobody replied.

It wasn't until three weeks after his senior season that Eastern Washington finally came through with a scholarship offer, beating out Idaho State.

"It was tough," Kupp said. "There's no feeling like that. I believed that I could play at the next level, but there is that voice in the back of your head saying, 'Well, right now no one else thinks that you can.' You know? But it didn't change my idea."

Kupp, who redshirted in 2012, was the FCS Offensive Player of the Year each of his last two seasons at Eastern Washington and had at least 90 catches, 1,400 yards and 16 receiving touchdowns in all four years. He finished his senior year with a Big Sky Conference-record 117 catches for 1,700 yards and 17 touchdowns, not to mention four other scores -- two passing, one rushing and one on a punt return. In four career games against Pac-12 opponents, Kupp averaged -- averaged -- 10 catches, 179 yards and 2.75 touchdowns.

"Growing up, all his life, people wanted to maybe label him, and he always did more than what people expected," said Baldwin, who has known Kupp since his sophomore year of high school. "He really wasn't any sort of one-trick pony. He could do anything within the receiver game and other things. He can get behind defenses, he can run underneath, he can catch screens, run after the catch, it didn't matter."

The Rams quickly fell in love with Kupp. They sat down with him for a formal, 15-minute interview at the scouting combine in Indianapolis and new head coach Sean McVay said, "You felt like you were almost talking to a receiver coach." When Kupp left the room, McVay turned to his actual receivers coach, Eric Yarber, and told him, "You're lucky we just hired you."

"You watch him play, you see he's got those pre-snap plans that, a lot of times, you don't see," McVay said of Kupp. "He is one of the more polished college receivers that I've evaluated coming out in a while."

Kupp ran an underwhelming 4.62 40-yard dash, but his times in the 20-yard shuttle (4.08 seconds) and the three-cone drill (6.75) were elite. He comes out of his breaks quickly, runs routes precisely, knows how to get open and has great hands. It was evident throughout the offseason program, and now the Rams are counting on Kupp to be a reliable security blanket for franchise quarterback Jared Goff, who badly needs one.

Through college, Kupp studied three wide receivers: Larry Fitzgerald, Antonio Brown and A.J. Green, all of whom do it differently.

After graduating, he studied the three main NFL offenses: Air Coryell, West Coast and Erhardt-Perkins.

He'll be ready for whatever the Rams throw at him.

"I don't have a single doubt in my mind that he will have an amazing impact in an NFL offense," Baldwin said. "I've never seen him get defended by anyone. I've never seen him struggle. I mean, it's been consistent, no matter who we played, no matter who it's against. And he's got a drive and a mindset that he's not going to allow himself to not have success."