AMHERST, N.Y. (AP) — After playing a role in convincing star linebacker Khalil Mack to return for his senior season rather than declare for the NFL draft last month, University at Buffalo coach Jeff Quinn wasn't done addressing his defense.

Unveiling the Bulls' 18-player signing class on Wednesday, Quinn announced he added two junior college transfers who have the potential to make immediate contributions to an already sturdy unit.

Defensive end Tedroy Lynch, who played at Lackawanna College in Pennsylvania, is expected compete for a starting job left vacant after the Bulls lost Steven Means to graduation. Lynch was credited with 13 tackles for loss, including 9 ½ sacks last season.

And then there's the addition of linebacker Blake Bean, who spent the past two seasons playing for Butler Community College in Kansas, where he was part of a team that went 22-2. Bean is already enrolled at Buffalo and will have two years of eligibility remaining.

The two will join a defense that finished second in the Mid-American Conference in yards allowed last season. And it's a unit that will include Mack, a two-time all-conference first team selection, who has already set school records for forced fumbles (11) and tackles for loss (56).

Excited as Quinn was about his latest additions, he couldn't overlook Mack's decision to stay.

"I think the No. 1 recruit in this was Khalil Mack," Quinn said.

The coach played a role in Mack's decision, by traveling to Florida last month to meet with the player and his family. Quinn came prepared, saying he contacted the NFL to have the league complete an evaluation of where Mack might rank among draft prospects in April.

Quinn wouldn't divulge where the NFL had Mack ranked, but said he shared the information with the player to help him make a decision.

"I told him, 'I know the NFL's there. It's not going anywhere. It's going to be there another year,'" Quinn said. "I also told him, 'You've got some opportunities to continue leading this program and be a great player and establish yourself with another year of development.'"

The Bulls are finally showing signs of improvement as Quinn enters his fourth season.

Buffalo is coming off a 4-8 finish in which it closed last season by winning three of its final four games. That's a step up from Quinn's first two seasons, in which the Bulls went a combined 5-19.

"We finished very strong last season, and they're ready to build on it," said Quinn, who has a majority of his starters returning. "They're not going back to where it once was. They're moving forward."

Of the Bulls' 18 signings, 11 are defensive players, six offensive and he also signed long-snapper/linebacker Corbin Grassman.

Among the Buffalo's more notable recruits is Jacob Martinez. He had 1,007 yards rushing and 19 touchdowns and 1,181 yards passing and 12 scores last season playing for Bozeman High in South Port, Fla. Quinn projects Martinez to play receiver.