The San Francisco 49ers had the best defensive line in the NFL last season, but they apparently want to see more from a former first-round pick before they make the ultimate decision to re-sign him. On Friday, Tom Pelissero of the NFL Network reported that the 49ers are declining the fifth-year option on defensive lineman Solomon Thomas.

Thomas was selected with the No. 3 overall pick in the 2017 NFL Draft out of Stanford. He actually hit the ground running in his rookie season, recording a career-high 41 combined tackles and three sacks despite starting in just 12 games. He started 13 games in his second season, but recorded just 31 combined tackles and one sack. While the 49ers went 13-3 and made it all the way to Super Bowl LIV in 2019, Thomas started just three games and recorded a career-low 21 combined tackles and two sacks. 

The 49ers did trade away DeForest Buckner to the Indianapolis Colts for a first-round pick this offseason, but they used that pick to select defensive tackle Javon Kinlaw out of South Carolina. As CBS NFL Draft writer Chris Trapasso noted in his defensive line class breakdown last month, Kinlaw really is in a class by himself among linemen in this class. At 6-foot-5 and 324 pounds with long arms, an incredible first step, stunning burst-to-power and counters off his awesome bull rush, he checks all the boxes trait-wise. In three seasons at South Carolina, Kinlaw recorded 82 total tackles, 17 tackles for loss and 10 sacks. Last season, he was named First-Team All-SEC after recording a career-high 35 total tackles, six tackles for loss and six sacks. 

He may be a perfect replacement for Buckner, but the 49ers also want to see Thomas step up his game in 2020. 

"We brought in (Javon) Kinlaw, but everybody who's watched us knows we rotate a lot of players there," 49ers general manager John Lynch said, via NBCSports.com. "We believe in going as hard as they can, and then we'll rotate, kind of like hockey lines."

"Solomon's going to be a big part of that rotation."