CINCINNATI -- The departure of Cincinnati Bengals left tackle Andrew Whitworth essentially came down to long-term security, according to his agent Pat Dye.

Whitworth agreed to a three-year deal Thursday with the Los Angeles Rams. The deal is worth $36 million with $15 million guaranteed.

The Bengals' best offer was a one-year deal worth $10 million, Dye said, refuting reports that the Bengals were willing to go as high as $11-12 million. The possibility of a second year was not on the table.

Whitworth will make $7.5 million in base salary in Year 1 with a $5 million signing bonus up front, essentially giving him almost $13 million in salary in 2017. He has the opportunity to make up to $24.5 million over the first two years of the deal.

What interested Whitworth the most was the stability of a longer deal in what could be his last contract. At 35, Whitworth is the oldest left tackle in the league.

The Rams were willing to guarantee $2.5 million in the second year of his contract, giving him a much better chance of being on the team by then. By guaranteeing a portion of his 2018 salary, the Rams would have to absorb several million if they released him after only one year, including the prorated portion of his signing bonus, which would immediately accelerate into that year's cap.

That would mean around $5.8 million in dead money for the Rams if Whitworth is cut in 2018, which is a significant investment.

It was clear there was no such job security with the Bengals, who drafted two tackles in the first two rounds of the 2015 draft in preparation for Whitworth's departure. The Bengals have preferred to go year to year on Whitworth's contract due to his age. His last contract extension was a one-year deal signed in 2015 worth $9 million.

The Bengals will now move on with Cedric Ogbuehi at left tackle. The Bengals will lose a team captain who was second only to Andy Dalton in the amount of offensive snaps taken since 2012.

The Rams were interested in obtaining Whitworth for not only his play on the field, but for his off-the-field impact as well, seeing him as a mentor to their young offensive linemen.

"They really made him feel wanted," Dye said.

Dye said it was a difficult decision for Whitworth, who has been in Cincinnati since the Bengals selected him in the second round of the 2006 draft and has raised his family there. If the contract terms had been close to what other teams offered, Whitworth would have accepted Cincinnati's deal. However, the Rams' offer was significantly more competitive.

"Andrew loves it there, loves the Bengals organization, he loves [coach Marvin Lewis], the fans, the city," Dye said. "If this thing had been equal or even close to equal, he would have loved to stay there."