If you are looking for a basis for optimism about this Phillies season, 2015 is a pertinent year. At the time, rebuilding projects in Houston and Chicago were at a juncture similar to the one the Phillies' is at now. Both teams were entering their fourth seasons under the command of front offices that had been hired to rebuild the roster from the ground up. The Astros, under Jeff Luhnow, had won 70 games the season before. The Cubs, under Theo Epstein, had won 73.

At the start of the regular season, oddsmakers in Vegas had set the over/unders for Chicago and Houston at 81.5 and 73.5 wins, but by the end of it, the two teams had eclipsed their projected totals by a combined 29 games, the Astros winning 86 and the Cubs 97, and both qualified for spots in the postseason.

The disparity between the preseason projections and the actual results was an example of the uncertainty that the Phillies now face. Like them, the Cubs and Astros knew that they had a talented crop of hitters about to break into the majors, with blue-chippers like Carlos Correa and George Springer in Houston and Kris Bryant, Jorge Soler, Addison Russell, and Kyle Schwarber in Chicago. The eventual success of both teams was in large part due to those players performing up to their potential.

But both teams also benefited from less expected contributions, particularly in their rotations. In Dallas Keuchel, the Astros got a Cy Young-winning season from a pitcher who just two years earlier had a 5.20 ERA and 38 career starts. In Collin McHugh, they got  200 innings from a guy they'd claimed off waivers the season before. The Cubs, meanwhile, got breakout performances from Jason Hammel and Kyle Hendricks: one, a 32-year-old veteran with a career 4.60 ERA, the other, a 25-year-old eighth round draft pick out of Dartmouth who they acquired in a salary dump trade

In order for the Phillies to significantly outperform their 76.5-win over/under in 2018, they will likely need a similar overachieving performance from one of the wild cards on their roster. While there's a good chance that they are still one year away from making serious noise, you could have said the same thing about both the Cubs and Astros back in 2015.

In a lot of ways, the Phillies lineup parallels the Cubs' at that juncture: Rhys Hoskins could be Anthony Rizzo, who was coming off a breakout 2014 season in which he posted a .913 OPS with 32 home runs. Scott Kingery might not be the can't-miss blue-chipper that Kris Bryant was before earning his promotion and hitting 26 home runs with an .858 OPS as a rookie. But J.P. Crawford could be better than Russell, who wasn't all that great at the plate as a rookie, striking out 149 times with a .696 OPS in 523 plate appearances. And Nick Williams and Aaron Altherr could be better than Soler, who posted a .723 OPS with 10 home runs in right field. Factor in Odubel Herrera and Carlos Santana for Dexter Fowler and Chris Coghlan and you can at least see a scenario where this Phillies lineup is equal to those Cubs.

As for the rotation, Jake Arrieta might not be the pitcher he was for the Cubs in 2015. And Aaron Nola might not be the one that Jon Lester was. But they are a formidable 1-2 punch with plenty of upside. It's the other three spots in the rotation where the Phillies need some pleasant surprises like the Cubs got in Hendricks and Hammel.

In that sense, the two players with the greatest potential to impact their season might be righthander Vince Velasquez and Nick Pivetta. Velasquez, in particular, is the wildest of wild cards, in a lot of different senses of the word.  After a 2016 season in which he logged 131 innings in 24 starts with a 4.12 ERA, and an excellent strikeout rate of 10.4 per nine innings, there was some reason to hope that he could improve his command and establish himself as a legitimate big-league starter. Instead, he saw his strikeout rate drop to 8.5 K/9 and his walk rate rise by nearly 50 percent to 4.3 walks-per-nine while he averaged less than five innings per outing in 15 starts before the Phillies shut him down.

In all likelihood, this will be the season that determines Velasquez's future as a starter, a role in which he has finished six innings in just 22 of his 46 career starts. When the Phillies acquired him from the Astros in the Ken Giles trade a couple of years ago, some scouts pegged him as a future late-innings reliever. Even that might be ambitious given the struggles he has had commanding his fastball (opposing hitters have a .776 OPS against him the first time through the order, so it isn't as if Velasquez's problems are related to the length of his outings). It will be interesting to see how Gabe Kapler and the front office decide to proceed if Velasquez continues to slog his way through five-inning performances. At this point, there is nothing the team needs more than another reliable starter. If Velasquez somehow became that guy in 2018, it would have a huge impact on their prospects.

Like Velasquez, Pivetta has a big arm that he struggled to harness last season, when he got through six innings in nine of his 26 starts. He averaged 9.5 strikeouts per nine innings, which ranked in the top fourth of the 47 NL starters with at least 130 innings pitched. But he walked batters in 9.8 percent of his plate appearances, which was the fifth highest mark. The 1.7 home runs he gave up per nine innings was the second highest in the NL, while his 6.02 ERA was the highest.

Yet a lot of people in the Phillies organization are quietly optimistic about the 25-year-old righthander's prospects this season. In his last six starts of 2017, Pivetta posted a respectable 4.36 ERA with 34 strikeouts, 12 walks, and four home runs in 33 innings. Not great numbers, but solid enough where a full season of such production would give them 175 innings of a good bottom-of-the-rotation starter.

There are plenty of other wild cards with the potential to move the season's needle. As of the start of this week, Jorge Alfaro had struck out in just 21.9 percent of his plate appearances this spring after doing so in 28.9 percent last season. If he gave the Phillies another righthanded bat with middle-of-the-order production — say, a full season of the .874 OPS and five home runs he produced in 114 plate appearances last season — that would qualify as a significant development. So, too, would a return of the Maikel Franco who posted an .840 OPS with 14 home runs in 335 PAs as a rookie.

The pendulum swings both ways, of course. With youth comes uncertainty. We still have little idea what Crawford, Kingery and Williams will become. History suggests the Phillies aren't there just yet. But it also suggests that you can't completely rule it out.