CHICAGO -- Nick Castellanos quickly won over the Cubs' clubhouse and the team's fan base last summer.

After coming over in a mid-summer trade, Castellanos treated every day like Opening Day, churned out hit after hit after hit, and he did not hide his emotions in big moments. Cubs fans will never forget the outfielder's celebratory bat slam after launching a homer against the rival Brewers in August.

Castellanos' spark was not enough to ignite a trip to October, and now a reunion with the North Siders is no longer on the table. Castellanos on Monday officially signed a four-year contract with the rival Reds, who have had a busy offseason and will head into 2020 as a real threat in the increasingly competitive National League Central.

Here is a look at the implications of Castellanos' free-agent decision for the Cubs:

1) The waiting game

One issue that has kept the Cubs' offseason in a holding pattern has been the pending outcome of the service-time grievance filed by Kris Bryant. The grievance -- stemming from the timing of his promotion to the Majors in 2015 -- is being examined by an arbitrator, whose decision will result in Bryant either staying eligible for free agency after '21 or hitting the open market next offseason.

Bryant's trade value would be directly impacted by that decision. And, given the Cubs' apparent budget limitations (the team's payroll projects to be slightly north of the $208 million luxury-tax threshold), trading Bryant would've been a potential avenue for more realistically pursuing a free-agent like Castellanos.

With that ruling still unannounced, Castellanos opted against staying in his own kind of holding pattern. Now, there are no impact bats of his caliber left on the open market. So, if Chicago makes a major trade between now and Opening Day, it will no longer be about freeing up funds for a free-agent pursuit, but more about building a contention bridge for future seasons.

Given how long the Cubs have waited, it may now make more sense for the team to keep the group intact and use the first four months to evaluate its roster. At the July 31 Trade Deadline, Chicago can then balance contending with future planning and managing the payroll.

2) The reality in right field

The perfect-world preference for the Cubs has been to keep Jason Heyward in right field, where he is a Gold Glove-caliber defender. Moving Heyward's contract was always an extremely unlikely scenario this offseason, so Chicago's best approach was always to try find a way to maximize his production. That means using Heyward mostly against righties, against which he hit .264/.365/.466 with 19 of his his 21 homers last season.

For the other side of what should be a flexible platoon, the Cubs recently reached a one-year agreement with right fielder Steven Souza Jr. Expect Souza to see the bulk of his plate appearances against lefties (108 wRC+ in his career) to help balance out the lineup. With the current roster, Bryant is another option to potentially move out to an outfield corner on a day a lefty starts.

3) Castellanos vs. Schwarber

If the Cubs wanted to avoid exposing Heyward to center more than absolutely necessary, then the question became: Would Chicago trade Kyle Schwarber to make room for Castellanos in left? Well, at less than half the cost ($7.01 million in 2020 for Schwarber vs. a $16 million annual salary for Castellanos), Schwarber could compare favorably to Castellanos offensively.

Here's a look at their production over the final two months of 2019:

Castellanos
Slash line: .321/.356/.646
Compiled: 16 homers, 21 doubles, 36 RBIs
Discipline: 4.4 percent walk rate, 20.9 percent strikeout rate
Advanced: 154 wRC+, 2.0 WAR (Fangraphs)

Schwarber
Slash line: .304/.394/.649
Compiled: 14 homers, 13 doubles, 38 RBIs
Discipline: 11.6 percent walk rate, 24.7 percent strikeout rate
Advanced: 163 wRC+, 1.9 WAR (Fangraphs)

4) Counting on comebacks

With no sweeping changes to the outfield, the Cubs will be hoping that Albert Almora Jr. and Ian Happ can rebound together to create a solid tandem in center field. Almora slashed .236/.271/.381 with a 64 wRC+ last year, but he had a .291/.329/.405 slash line over the 2017-18 seasons combined. Happ spent much of last season with Triple-A Iowa working on offensive adjustments, and then hit .311/.348/.672 in September for the Cubs. Age is still on their side, but there is also plenty of risk involved for the Cubs by standing pat in center.

5) The defensive picture

By keeping Heyward in right, the Cubs' defense has a chance to improve over the overall numbers from last season. Heyward moved to center to accommodate Castellanos' arrival last summer and posted minus four Defensive Runs Saved up the middle. In right, Castellanos had minus four DRS with the Cubs and minus nine overall on the season.

Schwarber was essentially a league average defender in 2019 (minus one DRS and a minus 0.9 UZR/150 in left field) and Heyward was an NL Gold Glove Award finalist in right (plus seven DRS). Up the middle, Almora took a step backward (minus five DRS in 765 1/3 innings), but his track record creates hope for a bounce back. Happ can hold his own in center, and both he and Souza rate as solid defenders in the corners.