LOS ANGELES >> Southern California defensive lineman Leonard Williams announced Monday he will skip his final year of eligibility to enter the NFL draft.

Williams has long been expected to forego his senior season for the draft, where he is likely to be a high first-round pick. Although Williams felt some reluctance about leaving USC after his first year under coach Steve Sarkisian, he announced his decision two days after the Trojans (9-4) ended their season with a win in the Holiday Bowl.

“This was a very hard decision for me,” Williams said in a statement issued by the school. “I love USC, Coach Sark and the coaching staff, my teammates and the fans, and I love the game of college football. It’s hard to leave all of that. I know life is never the same once you leave college. But I feel like it’s the right time for me to go. I feel like I’m ready. I’m looking forward to the new challenge that the NFL presents.”

Nicknamed “Big Cat,” Williams has been a dominant defensive lineman for three seasons with the Trojans, racking up 21 sacks and 36 1/2 tackles for losses. Despite attracting constant double-teams from offensive lines in the pass-happy Pac-12, he was second on the USC roster this season with 80 tackles and a team-leading seven sacks, earning second-team All-American honors.

The imposing 6-foot-5 end from Daytona Beach, Florida, was lured to the opposite coast by Ed Orgeron, the defensive line coach and interim head coach who left USC last year after getting passed over for the full-time job.

Sarkisian was grateful Williams remained committed this season to the Trojans, who beat Nebraska 45-42 in the Holiday Bowl on Saturday. Williams was named the bowl’s top defensive player with nine tackles and a sack.

“We wish Leonard the best of luck,” Sarkisian said. “We know he will represent USC well in his professional career. He was a great player here for all three of his years. Just like all of our players, Leonard is a Trojan for life and we will always support him.”

Williams has drawn comparisons to NFL lineman Richard Seymour, and he figures to be a valuable commodity in the upcoming draft for his gap-clogging and pass-rushing versatility.

Although he expressed conflicting feelings about leaving USC last month, noting he had never managed to beat archrival UCLA during his time with the Trojans, Williams realized he couldn’t realistically wait for a fourth shot.

“I’ll always be a Trojan,” Williams said. “Now, I get to be part of the great tradition of USC alums in the NFL. I’m excited to see what’s coming next for me.”

Williams is the first departure in the Trojans’ annual list of top talents declaring for the draft. Receiver Nelson Agholor and tailback Javorius Allen are among the top talents considering an early start on their NFL careers.

But quarterback Cody Kessler already announced he will return for his senior season immediately after the Trojans’ Holiday Bowl win. The two-year starter tied Matt Barkley’s USC record with 39 touchdown passes this year, throwing for 3,826 yards with just five interceptions.