On June 2, 2018, the Mets rolled out a lineup with José Bautista in left field, Kevin Plawecki at first base and Luis Guillorme at third base, eventually also giving pinch-hitting appearances to José Reyes, Adrián González and Jose Lobaton. They lost, 7-1, to the Cubs in extra innings, one of many wasted outstanding Jacob deGrom starts. 
That game may not have been exactly what new general manager Brodie Van Wagenen had in mind when he talked about "eliminating the ifs" and "[having] versatility on the roster that gives us depth," but it gets to one of the main points of this particular Mets offseason. No, they haven't come away with Manny Machado or Bryce Harper, but they have managed to attack one of the main problems the 2018 group had: a lack of depth. They've raised their floor.
Another way to put that is like this: An obvious and effective way to win baseball games is to have good players, but a more subtle yet also quite effective method is to not have unproductive players.
It sounds like the same thing, but it's really not. Stars are great, obviously. The past three World Series champions had Mookie Betts and J.D. Martinez (2018 Red Sox); Justin Verlander and José Altuve ('17 Astros); and Kris Bryant and Anthony Rizzo ('16 Cubs). You can't win without star players, which is why Harper and Machado are so appealing. But those World Series winners also had valuable role players like Steve Pearce, Jake Marisnick and David Ross. They had depth, lots of it.
If you want to see the importance of depth, look no further than the Dodgers and Astros, arguably the two most consistently good teams over the past few years. Sure, they have stars. But they've also managed to cover for injuries to Clayton Kershaw, Corey Seager, Justin Turner and Carlos Correa, among others. Losing top players was more of a speed bump than a season-ending calamity, as it's been for other clubs. That's how championships are won. 
There's a pretty clear way to show the relationship between having fewer unproductive players and winning games, and that's by taking the stars out of the equation. We can prove that pretty easily by looking at how much playing time teams gave to players who didn't have much to offer in 2018. The quick-and-dirty way we'll do that is to use FanGraphs' Wins Above Replacement model and find non-pitchers (minimum 10 plate appearances) who put up a negative WAR in '18.
This isn't perfect because we're treating everyday players the same as part-timers -- we'll get to that in a minute -- but the takeaway here ought to be clear.

On the right, five of the six teams with the fewest negative-value players made the playoffs. (The Cubs had just one, backup catcher Chris Gimenez, who had only 32 plate appearances for Chicago. The Dodgers and Astros being tied for second fewest is the least surprising outcome.)
On the left, the seven teams who had more than nine such players all finished below .500. We haven't even talked about stars yet; it's just that it's all but impossible to win if you have too many players who aren't carrying their weight.
(About the surprising position of the World Series champion Red Sox: That's largely because three of those eight were their catchers Sandy Leon, Christian Vázquez and Blake Swihart, who combined to hit just .202/.255/.294 in 755 plate appearances. This also includes Eduardo Núñez's .265/.289/.388, as well as the limited contributions from Hanley Ramirez before he was released. In addition, three of those players -- Brandon Phillips, Sam Travis and Dustin Pedroia -- combined for only 78 plate appearances. It helps to have superstars like Betts, Martinez, etc., to balance it all out.)
Look closer at those three teams on the left, the ones who had the most sub-replacement players. You'll see the 115-loss Orioles, which isn't surprising. You'll see the Marlins, Royals and Tigers, all of whom lost between 98 and 104 games last season and are not expected to contend in 2019. But you'll also see the Mets, who are very much trying to win this year, which explains some of their offseason moves.

In 2018, the Mets gave nearly 1,000 plate appearances to the following group: Reyes, Travis d'Arnaud, Jack Reinheimer, Phillip Evans, Ty Kelly, Guillorme, Gonzalez, Lobaton, Dominic Smith, Matthew den Dekker and Tomas Nido. This doesn't even count the 210 plate appearances given to Austin Jackson and his .247/.290/.348 line, since he barely squeaked past 0 WAR. (Only d'Arnaud, Guillorme, Nido and Smith remain in the organization; d'Arnaud is fighting for a backup job, and the other three are all ticketed for Triple-A in 2019.) That distinguished collection combined to hit all of .194/.257/.309 and were worth negative-3.7 WAR. 
So take the nearly 1,000 production-draining plate appearances from that group, plus the 916 more given to Jackson, Plawecki and Wilmer Flores (combined 1.1 WAR, .246/.311/.387), who each also have departed from the organization, and it gives us 1,831 times to the plate -- and a .220/.284/.348 line, negative-2.6 WAR. That's nearly a third of all non-pitcher plate appearances for the Mets in 2018.
The 2019 Mets are replacing that volume of plate appearances with contributions from newcomers Robinson Canó, Jed Lowrie, Wilson Ramos, J.D. Davis and Keon Broxton. Take a look at the 2018 production for those five new Mets as well as their 2019 projections:
2018 actual: 1,646 plate appearances, .274/.348/.445, 10.8 WAR
2019 projected: 2,127 plate appearances, .247/.318/.410, 8.0 WAR
Either way, that's much better. Conceivably an upgrade of 10-12 wins. And depending on health and how quickly first-base prospect Peter Alonso (No. 2 in organization, per MLB Pipeline) acclimates, manager Mickey Callaway may also have the option of calling Todd Frazier and Jeff McNeil off the bench on a daily basis, plus competent veterans Rajai Davis and Grégor Blanco likely a phone call away at Triple-A. Simply in terms of depth, the 2019 Mets should be markedly better than their '18 counterparts. 

If this sounds familiar, think about the 2015 Mets. You probably remember that group's run to the World Series as being fueled by the acquistion of Yoenis Céspedes, the emergence of Daniel Murphy and the the arms of Matt Harvey and deGrom, and that's all true. But before that team really took off, they had games like this one where the 3-4-5 in the lineup were Flores, John Mayberry Jr. and Eric Campbell. Where things really started to change was when the Mets acquired Juan Uribe and Kelly Johnson from Atlanta, the same day Michael Conforto was promoted for the first time.
Neither veterans were stars, but that wasn't the point. It gave the club a competent bench, and sometimes that's just as important. You need stars to win. You need depth and complementary players, too. Just ask Mike Trout, the best player of his generation, how many playoff games he's won without help (Hint: 0). 
Now it may not be enough. The Mets' lineup would sure look better with Harper or Machado. There are still open questions about whether the talented-but-fragile rotation has enough depth, because we haven't even gotten into how P.J. Conlon, Harvey, Drew Gagnon, Corey Oswalt and Chris Flexen all made starts for the Mets in 2018 -- 20 of them, or more than 10 percent of the season -- and combined for a 6.58 ERA. Plus, the National League East looks like a four-team cage match.
But if Van Wagenen wanted to minimize the "ifs," it sure seems like he's done that, on offense, anyway. As the Dodgers, Astros and Cubs have shown, depth matters. It matters matters more than ever. The Mets are trying to push themselves in the right direction.