The struggles didn't stop there, either.
After getting just one start with the big club and getting knocked around for five runs through a measly four innings, Happ found himself back on the farm, pitching for Triple-A Lehigh Valley and finishing up a rough year.
In his fourth season as a professional pitcher, a year mired by elbow problems, Happ would end up posting a 5.02 ERA in 24 starts at the Minor League level, and uncertainty began to creep in.
"It was a tough situation for me in general," Happ said. "I don't really like to get into the specifics, because I don't want to make excuses about anything. I would say, just in general, I wasn't 100 percent healthy, and I tried to battle through some things.
"It was tough on me physically and mentally. But I knew going into the offseason it was going to be a make-or-break situation."
Happ sure treated it like one.
The Spring Valley, Ill., native was one of the first players cut during Spring Training, but unlike the previous season, he didn't let setbacks affect him on the mound. Instead, he went back to Triple-A, pitched like the dominant pitcher the Phillies expected when they drafted him in 2004 and continued to impress when called up twice to the big club.
He impressed so much that now -- after being a September callup, landing a spot on the postseason roster and even pitching in a game during the playoffs -- he's got a legitimate shot to land a spot in the starting rotation for 2009.
What a difference a year makes.
"That's something I'm really proud of is being able to bounce back," Happ said. "I know that when I'm healthy, I can pitch very well. After several months of doing pretty well in the Minor Leagues, for the Phillies to give me another chance was huge. They gave me a couple of opportunities, and I'm really looking forward to sticking with them and being a more integral part of the team."
After a strong showing at Lehigh Valley, the 26-year-old was called up temporarily to replace a struggling Brett Myers in early July and got his long-awaited second chance. This time, however, he didn't let it slip, posting a 3.69 ERA in eight games -- four starts -- during two stints with the Phillies.
His biggest success came in September, when he posted a 2.41 ERA in five games -- two starts -- and was an integral part in the Phillies going 17-8 to sneak into the playoffs.
But Happ, who finished 8-7 with a 3.60 ERA in 24 Triple-A games in 2008, said he did most of his maturing while sitting in the dugout and witnessing, firsthand, the Phillies' magical run to a World Series title in October.
"I was talking to Jayson Werth one day, and he just kind of randomly said, 'Do you realize what happened here? Some guys wait their whole career to experience the postseason like this,'" said Happ, who gave up one run in three innings during his only postseason appearance -- Game 3 of the National League Championship Series against the Dodgers.
"I'd like to think it makes a difference [to be on a playoff team]. I think just being there, having the guys know me and recognize me and start having confidence in me. Obviously, you want the respect of your teammates, and hopefully I'm on my way to earning that. And it means a lot when you're out there on the mound and you know guys are counting on you."
When pitchers and catchers report to Clearwater, Fla., on Feb. 14, Happ will find himself competing against Chan Ho Park, Kyle Kendrick and Carlos Carrasco, among others, for the wide-open No. 5 spot in the starting rotation.
But another opportunity also presented itself in a bittersweet way earlier this month, when teammate J.C. Romero was suspended for the first 50 games of the season after testing positive for use of a banned over-the-counter supplement under Major League Baseball's Drug Policy. Romero's loss leaves a gaping hole for a left-hander in a Phillies bullpen that was the best in the NL in 2008 -- a hole Happ can also fill.
But, for the most part, Happ feels sympathy for Romero.
"It's super unfortunate for the Phillies' organization because he's one of the best in the game, and it's super unfortunate for him because I know how hard he works," Happ said. "I see him work and I see him prepare, and I know he's not trying to cheat anybody.
"It makes you think twice about what you stick into your body. It's tough, and I'll admit that it worries me sometimes."
But with an upcoming season filled with promise on the horizon, Happ has other things to worry about right now -- like the competition he'll face from players who've been around a lot longer than him.
Park has already said he's going to skip playing for Korea in the World Baseball Classic this spring because of how bad he wants to land that starter's spot.
Happ claims he wants it just as much.
"The goal is to be a starting pitcher," Happ said. "That's what I'm accustomed to, and that's 100 percent what I'm shooting for. This is what I do and what I love to do, and I'm going to give everything I can to win that spot.
"That fifth starter's spot is something I've been looking at since the last day of the season, so I'm looking forward to it."