2. Matt Chapman
Third base is an interesting position for the Cubs at the moment. Currently, their best defender at the position is Nick Madrigal who has managed to accumulate 7 defensive runs saved and 10 outs above average across 560 1/3 innings this year. His 83 wRC+ doesn't cut it for such an offense-heavy position though. Jeimer Candelario was acquired at the deadline to add extra firepower with a 118 wRC+ on the year, but he's had a bit of a rollercoaster career and, before going out with an injury, struggled mightily in Chicago.
Re-signing Candelario might not be a bad idea, but if the team really wants to make a big splash, Matt Chapman is the way to go. There are no questions about his defensive ability - the two-time Platinum Glove winner has been excellent at the hot corner yet again with 4 OAA. He's also paired that with another solid offensive season overall with a 112 wRC+, though there are warning signs as those results have largely been carried by a hot April and July.
There are reasons to be optimistic about Chapman offensively, though. Statcast shows he's one of the best hitters in MLB when it comes to barreling the ball and exit velocity and, although his strikeout rate is a bit high, he doesn't chase often. He also doesn't put the ball on the ground much either, coming in with a rate nearly ten percent below league average. Sportrac currently has him estimated at a four-year, $64.7 million deal which, for a stellar glove and a bat with high upside seems very reasonable.
It will probably cost a bit more than that to actually land Chapman, but there's an undeniable fit for him with the Cubs. With him in tow, especially if they re-sign Bellinger at first base, it would be hard to find a better defensive infield complete with Nico Hoerner and Dansby Swanson up the middle.