The San Francisco 49ers don't have much more time at their disposal if they want to strike a trade to help fuel their hopes of a second-half surge.

Tuesday sees the deadline for teams to make in-season trades, with the Niners and the rest of the NFL having until 4 p.m ET to strike deals.

San Francisco has, under Kyle Shanahan and John Lynch, traditionally been aggressive in buying at the deadline to improve its hopes of finally winning a sixth Lombardi Trophy, as offensive tackle Trent Williams noted on Monday.

"I keep an eye out for John and Kyle," said Williams. 

"They are super aggressive in doing anything to better the chances of us being a winning football team. So I know if there's a move to be made, they probably going to try to make it."

Yet the 49ers can't think solely about this year when assessing what to do at the deadline. They have to think about 2025, when the 49ers are likely to have the challenge of keeping an excellent roster together while also making quarterback Brock Purdy one of the highest-paid players in the NFL.

Key to their ability to strike that balance will be the amount of salary cap the 49ers rollover.

Teams are permitted to roll over 100 percent of their cap from one year to the next, and must tell the league if they intend to do so by 4 p.m. ET the day after the regular-season finale.

San Francisco, per Over The Cap, currently has a league-high $54 million in cap space. That gives the 49ers a lot of potential wiggle room in terms of salary they could take on in a trade but, with Purdy's extension looming, they may be reticent to add a contract that would eat significantly into their cap room and potentially damage their hopes of keeping the roster intact to their satisfaction while inking Purdy to a long-term deal.

That is not to say the 49ers will elect against making a move at the deadline, but a deal that sees them take on a low-cost rental is more likely than one that results in them acquiring a player with a big base salary.

Purdy won't be thinking about his contract right now, but it's part of the equation for the 49ers as they try to make the best decisions for the team's present and future at the deadline.

49ers presented with another opportunity to reunite with veteran starter from Super Bowl 58

It could make a lot of sense.