The San Francisco 49ers aren't ready to make any promises on the future of defensive lineman Arik Armstead, but general manager John Lynch and head coach Kyle Shanahan expressed on Monday that the team is happy with the progress the fourth-year player made this season.

"Yeah, we're very excited with the way he played," Lynch told reporters. "Now, Kyle coaches, he's the head coach of our team. He's also the game planner. So, while we spend a lot of time, this is our opportunity, we'll each take a couple of days off, we'll get back and really start to spend some time looking at our complete plan.

"I don't want to make any absolutes, 'Yes, he's going to be here,' all those things. But, we are pleased with the way Arik progressed and excited about his future."

The 49ers picked up Armstead's fifth-year option back in April, which means if they want to keep him in 2019 at the cost of $9.046 million in salary, they can. The option, however, isn't fully guaranteed until March. That means Lynch and Shanahan will have a decision to make before then.

"All those decisions aren't as simple as how do we feel about Arik, because if it was, then yes," Shanahan added. "Arik's done a good job, and you don't want to lose good players. Those decisions are based off of how do you want to balance and allocate all the money because you can't do whatever you want.

"What are the options out there? What's our depth chart look like? And what's the best way to do it? But, if it's as simple as just Arik, then yes, we really are happy with Arik."

Armstead had his best NFL season this year. He finished with career-highs of 48 combined tackles and three sacks through 16 games.

The 49ers made Armstead, who played college football at Oregon, the No. 17 overall draft pick in 2015. He finished the 2016 and 2017 seasons on injured reserve.