Lionel Messi and LeBron James have a lot in common. You know, beyond the fact that one of them looks like he was carved out of some impossibly dense space material, and the other needed human growth hormone to achieve a stature that would not be out of place at your local secondary school.

Messi and LeBron were both identified as epochal talents as teenagers, and they both surpassed impossible expectations. They've been brow-beaten for not having enough titles too, but more than all that, when they're at full flight, they dominate games in a similar, omnipotent fashion: LeBron can be the best scorer, creator and passer in any game, all at once. The same goes for Messi.

During the 2015 NBA Finals against the Golden State Warriors, the Cleveland Cavaliers attempted to leverage LeBron's greatness to an absurd degree. After injuries to the team's second- and third-best players, the Cavs basically put the ball in James' hand every possession and let him run the shot clock down to zero and decide each possession on his own. It almost worked. The Cavs took a 2-1 lead, only to lose the series in six games, and James became the only player in league history to lead a Finals series in points, assists and rebounds.

James was then 30, the same age as Messi at the start of the 2017-18 season. Strangely enough, that's right when Leo started doing his LeBron impression.

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Messi has led La Liga in both goals and assists each of the past two seasons, which is something he hadn't done before. Meanwhile, Barcelona won La Liga by 14 points in 2017-18 and 11 points last year, marking the first time they've won the league by at least 10 points in consecutive seasons this century.

Despite Barcelona's domestic dominance, they've failed spectacularly on the biggest stage. Each result is easy enough to write off on its own, as just one goal from Barca in the second leg against Roma or Liverpool would have put Messi & Co. through to the next round of the Champions League. In both games, they conceded more goals than expected and scored fewer; just a tiny bit of good luck in a single moment, and this piece probably has a significantly different tone.

Perhaps, though, building a team that's so incredibly reliant on one player makes you vulnerable to the remontada. By design, Barcelona need Messi to play well for the team to play well.

According to TruMedia data going back to 2010, Messi created a career-high 24.2% of Barcelona's chances (assists plus key passes) when he was on the field in 2017-18. Barca were even more reliant on him to put the ball on goal, as he accounted for 39.2% of their shots, his second-highest proportion since 2010. This past season, Messi upped his importance as a creator (28.3%) while maintaining a similar proportion of shots (37.9%). If you add both numbers, Messi was responsible for 63.4% of Barca's total shots in 2017-18 and 66.2% last season. This is unprecedented, as the previous high was 55.5% in 2012-13.

Really, can you blame Ernesto Valverde? If Messi is the best soccer player of all time, why not try to make sure that said best player is influencing the game as often as possible? As Sir Alex Ferguson once said, "The work of a team should always embrace a great player, but the great player must always work."

Messi's influence isn't limited to shots, either. According to data from STATS LLC, Messi is the only player in Europe's top five leagues who, per 90 minutes, averaged at least three shots, two dribbles, four final-third entries and one shot-assist last season. Those are the four main facets of play when a team is in possession: moving the ball up the field, unsettling defenses with a take-on, creating attempts and taking shots. They aren't cherry-picked filters, either: Messi soared beyond each baseline, averaging 5.4 shots, 3.8 dribbles, 6.2 final-third entries and 2.9 shot assists.

His fingerprints are on just about everything.

"In the past three seasons of Europe's top five leagues and the Champions League, players had 748 stints of at least 570 minutes or more as wingers, attacking midfielders and second strikers," said Daniel Altman, formerly an analyst with Swansea City and the creator of smarterscout.com, an online platform for advanced player metrics.

"Only three of those stints featured a 70% share or more in the moves leading to goals, shots and expected goals: Jonathan Viera at Las Palmas in 2016-17 and Lionel Messi in both La Liga and the Champions League in 2018-19. That's stunning."

As of now, Messi's singular brilliance has worked out well for him and for Barcelona ... except for one weekday night in Rome and another one in Liverpool.

A good performance isn't necessarily enough in these individual games, either: Messi created two big chances, which Opta defines as a "situation where a player should reasonably be expected to score," in the 4-0 loss to Liverpool. In the Champions League games Messi played in this past season, Barcelona were 6-0-0 when he scored or assisted and 1-1-2 when he didn't. If we apply three points for a win and one for a draw across all games in Europe the past three seasons, Barca average 2.69 points per match with a Messi goal or assist and just 1.30 points without.

It's Messi, or it's nothing.

"The overreliance tends to lead to predictability of playing style, as well as the obvious ability of the opposition to limit supply," said Ben Darwin, the founder of Gain Line, a sports analytics company.

He added: "Teams can have a habit of getting what we call 'top heavy,' i.e. all the focus is on a few senior guys critical to the success of the team. Overreliance in these cases can be quite dangerous, and the fallout of an injury to that player can be pretty disastrous."

Messi's continued health despite his slight frame is one of the under-appreciated aspects of his storied career -- he has appeared in at least 30 La Liga matches in each of the past 11 seasons -- so the soccer world takes his production as a given. But everyone's body starts to break down at some point. Just ask LeBron and the Los Angeles Lakers. Plus, even if Messi doesn't get hurt, he's going to slow down eventually, right? Most players peak between 24 and 28, and the fact that Messi is four years beyond that and has yet to really decline is the main reason Barcelona remain one of the two or three best teams in the world every season.

They have an irreplaceable player carrying an unprecedented load while the downside of the age curve looms. It's unlikely that Barcelona (or any other club, for that matter) will ever have another player capable of reproducing what Messi is doing right now, and that creates a conundrum -- one that everyone else would love to have but a conundrum nonetheless: Do you sacrifice the future and go all-in on the last few years of an all-time great by surrounding him with in-their-prime stars? Or do you fill the squad with young talents who can contribute now and will hopefully be reaching their peaks when Messi finally falls from his?

The deals for Ousmane Dembele and Philippe Coutinho, two proven youngsters who were just entering or still years from their primes, seemed to suggest the latter. Same goes for the recent move for the 22-year-old Frenkie De Jong. However, the rest of this summer's rumored business points in the other direction. Sources have told ESPN that the club is considering signing both Antoine Griezmann (28 years old) and Neymar (27), with potentially Dembele, Coutinho and 25-year-old Samuel Umtiti heading out as makeweights. Barcelona had the fourth-oldest average starting eleven in La Liga last year. If those moves come off, they're only going to get older.

"It seems Barcelona have not gone back to the well," Darwin said. "One of the biggest things we find is that a pressure to reproduce success means that the clubs will not return to a youth policy but look for players who can deliver now."

If Neymar and Griezmann both come to the club, Barcelona are essentially saying that now is all that matters. If they win the Champions League, it'll be hard to argue with the results. But by pushing all of their chips into the present, they're ensuring that the transition into a post-Messi world especially painful.

Remember what happened in Cleveland when LeBron left for Los Angeles? With him, the Cavaliers made the Finals four years in a row. In their first year without him, they won 19 games ... in an 82-game season.