The Tampa Bay (Devil) Rays never finished a season with more than 70 wins prior to 2008. Despite several years of top draft picks, a combination of bad luck (Josh Hamilton), bad injuries/illness (Rocco Baldelli) and bad eggs (Delmon Young, among others) left them with a young, unproven and somewhat unheralded team heading in 2008. Their Starting Pitching was all 26 or younger. Their position players weren't quite as callow, but they did feature several young players at key spots, none perhaps more impactful that Evan Longoria, who won the Rookie of the Year award and established himself immediately as the key to the current Rays fortunes.
In the off-season leading into 1993 I doubt anyone outside Veterans Stadium expected much from an old Phillies team coming off 6 consecutive losing seasons. It was a team full of role players nearing the end of careers, castoffs who never quite lived up to their potential and a 23 year old Shortstop who never again put up numbers as good as his rookie year (Though he had a nice season with the Devil Rays near the end of his career). Kevin Stocker's rookie line would look mighty good at any number of positions on the field. He appeared to be quite good, in spite of a lack of power, putting up a .324/.409/.417 line over half a season. The Phillies used this line and a number of other career or near career seasons across the line up to propel them to 97 wins and the World Series (where they subsequently lost to Mitch Williams).
There are a range of contributions rookies can make from those above to Marty Bystrom's handful of starts at the end of the 1980 season. So, who can step in and help the Phillies in 2014? Cesar Hernandez is a strong runner, has a good eye and makes consistent contact as a hitter. He rivals Ben Revere in the power department, but in the event Revere has another season lost in part to injury, Hernandez is the kind of player who could put in a Kevin Stocker-like line. Very little power, but potentially very good AVG and OBP numbers, with plenty of steals and probably less than stellar Defense (no fault of Cesar's, he's not a Center Fielder). Hernandez playing anywhere else would be a detriment to the prospects of the parent club at this point. If he starts for an injured Utley at Second, he'll do fine on D and getting on base, but you lose Utley's far better power. Cesar simply doesn't have enough arm for the left side of the diamond, so the chances of any big contribution here lies in Revere being unavailable. I'm not sure replacing Revere with Cesar is preferable, but I could see a big year from Hernandez in the same way '93 was for Stocker.
Another possibility would be that it's late May 2014 and while rounding First Base, Ryan Howard's leg tendons, all of them, give up and fall out simultaneously. The good news is that Dr. James Andrews rebuilds the Big Piece's leg, Robocop style. That's great, but as you can imagine recovering from partial cyborg surgery is long and intensive. Howard misses the rest of 2014, but is fully healthy in 2015 (though sadly no faster. If you've ever watched Robocop, you're aware that Robocop moves like a septuagenarian making a bee-line for the rhubarb pie stand at the country fair). Not to fear though, Maikel Franco is currently killing the ball in Reading. In order to avoid starting his service clock and to give him a few weeks in Lehigh Valley to see if he can stay hot, the Phillies start John Mayberry Jr at First for two barely watchable weeks before calling up Franco. Fueled by a BABiP approaching .400, an unusually high BB rate of 10% and a league full of Pitchers unfamiliar with his tendencies and weaknesses, Franco feasts on fastballs as fielders fail to field flies that fly far from gloves, like frozen ropes over outfield walls. By season's end Franco has put up a line of .290/.370/.580 and walked off with the Rookie of the Year award. In 2015 he settles into what will be roughly, his career line a very respectable .270/.330/.480.
A third scenario I could foresee is that Jesse Biddle's 2013 proves to have been a fluke caused by whooping cough. In 2014, feeling stronger and able to grip his Curve properly, Biddle goes on a tear in early 2014. Mowing down hitters with new command of his pitches and a Curve that buckles knees. By mid-season, Roberto Hernandez moves into a bullpen role as Jesse Biddle makes his first Major League start and establishes himself as a solid middle of the rotation starter behind Lee and Hamels (making the Phillies rotation L-L-L-R-R). Biddle wins 10 games in his half season of work and is the 3rd starter for the Phillies' playoff appearances (remember, this is all pie in the sky theoretical).
Probably the most likely scenario of all is that, borderline rookie eligible, Cody Asche establishes himself as a viable Major League Third Baseman. Carrying a line very similar to his 2013 .278/.327/.454 line and playing a league average third base in terms of defense. The future continues to look bright as the Phillies get good seasons in the minors from Kelly Dugan, Aaron Altherr, Andrew Knapp, JP Crawford and First Round pick Brady Aiken (I'm full of predictions here).