SANTA CLARA, Calif. -- San Francisco 49ers general manager John Lynch has only been on the job since 2017, but he already has been faced with plenty of difficult decisions.

Speaking for the first time since the NFL combine in a pre-draft video chat Monday afternoon, Lynch said agreeing to deal defensive tackle DeForest Buckner to the Indianapolis Colts for the No. 13 pick in this week's NFL draft on March 16 was the hardest choice of his executive career.

"Probably the toughest thing I've done since I've been a general manager here and that's the trade with DeForest Buckner," Lynch said. "It's a difficult part of this business. One that I don't think you can really prepare yourself when you move on from a player who embodies everything that you want to be about. We spend a lot of time talking about what's a 49er to us, and DeForest Buckner embodied that in every way both on and off the field."

Buckner had been a foundational player for the Niners since they used the No. 7 pick in the 2016 NFL draft on him. Since then, Buckner missed just one game in four seasons, playing the third-most snaps in the league among defensive lineman during that time. He recorded 28.5 sacks in the regular season and was named the team's Bill Walsh Award winner in February, an honor given to the Niners player who "best represented the standard of professional excellence."

Despite all of that productivity, Buckner's price tag ultimately became too much for the Niners to swallow. Earlier in the offseason, Lynch and coach Kyle Shanahan had placed an emphasis on trying to keep as much of the NFC championship roster together as possible while acknowledging there might have to be trade-offs to make that happen.

Ultimately, it came at the expense of Buckner.

"We talked about we wanted to do our best to keep this team together," Lynch said. "It became apparent in the discussions with [Buckner] that that wasn't going to be a possibility along with keeping our team together as we wanted to do so.

"The Colts entered the picture with a pick, not only a first-round pick but in the upper half, and we weighed that with the opportunity to sign other guys. It was one of those business decisions that's so tough. [Colts GM] Chris Ballard is a guy I respect as much as anybody in this business, and I think we were able to get something done; but it's not without a heavy heart that we move on from [Buckner] because he's such a big part of what we've been able to do. We wish him and his family nothing but the best."

Upon finalizing the trade, Buckner signed a four-year, $84 million contract with the Colts, while the Niners used some of the savings to re-sign the likes of defensive ends Arik Armstead and Ronald Blair III, free safety Jimmie Ward and offensive lineman Ben Garland.

Lynch said the Niners will turn to in-house options such as D.J. Jones, Solomon Thomas, Kevin Givens, Jullian Taylor and Kentavius Street to help fill the void left by Buckner. The 49ers also explored some free-agent options at defensive tackle, though Lynch said "nothing came to fruition" on that front.

Of course, the team also holds that 13th pick, which could bring a replacement at defensive tackle such as Auburn's Derrick Brown or South Carolina's Javon Kinlaw, should either fall to that point in the draft.

Regardless, Buckner leaves behind big shoes to fill.

"We have the 13th pick, what are we going to do with it?" Lynch said. "We've got to do great things because we certainly lost a great player."