The right-hander logged just over 60 innings this past season, making four stops throughout the Cubs' organization: Class High A Daytona to begin the year; Double-A Tennessee from late April through late June; Chicago, for his major league debut; and Triple-A Iowa, where he would end the year.
Sixty innings may not seem like much, but as someone who had previously undergone major shoulder surgery and missed over a year's worth of action, the full season from start to finish began to take its toll on the 23-year-old Petrick.
With the year coming to a close, Petrick was clearly showing signs of late-season fatigue. Such was the case in a late-August match-up against Triple-A New Orleans in what would turn out to be his final appearance of the season.
Petrick faced seven batters, scattering four runs (three earned) on three hits, including two home runs in what essentially amounted to batting practice.
By then, Petrick's velocity was noticeably down from its form from earlier in the year. He went from consistently reaching 93-95 mph on the radar gun during the summer to often hovering around 87 mph late in the season.
And so when the Cubs began expanding their roster to include September call-up's, Petrick's name was absent. The only thing left was to shut Petrick down once and for all in 2007 and close the book on a generally successful season overall.
Over a month later, Petrick visited Dr. Craig Morgan, an orthopedic surgeon in Wilmington, Del., to get his shoulder examined. Morgan had good news.
"There was nothing structurally wrong," Petrick said of the report he received from Dr. Morgan. "It was just a couple of tight muscles that I need to get stretched out before I start throwing in December."
Petrick said the velocity drop was the biggest signal that something was becoming amiss. He noticed it himself, and teammates also commented on it.
"Clay Rapada, Kevin Hart and those guys said, ‘you don't look the same as when you first came down from the big leagues,'" recalled Petrick.
Iowa's pitching coach, Mike Harkey, didn't appear to be quite as fazed.
"To me, it's only down from where it was in Spring Training," Harkey said in August when asked about the drop in velocity of two Iowa pitchers.
"A lot of guys' velocities are down this time of year," Harkey noted.
Petrick had plenty a reason to be concerned then, but now having received the OK from Dr. Morgan, he has plenty a reason for optimism.
The year 2007 was an adventurous one for Petrick, who was put on notice back in Minor League Spring Training that he would be moving into the bullpen.
Petrick had made 63 starts in the Cubs' farm system from 2002-2006 after being selected in the third round of the 2002 draft from Morris High School near Chicago.
This season, he made 41 appearances – all in relief.
"I found myself throwing fastball and slider," Petrick said of his work in the bullpen. "I found a slider that I knew I could throw at any point in the count and with the confidence that they weren't going to hit it. That was my out pitch, and the pitch that I threw when I needed a strike or a swing."
Petrick said he threw "about 10 changeups all year," but that, "they came at good times."
All in all, Petrick said he was pleased with the strides he made in his first year pitching in relief, and with the ascension he made from A-ball to Chicago.
Daytona was not where Petrick wanted to begin the year, however, and he admits he was somewhat upset when he found himself back there out of Spring Training.
"I was thinking, ‘Why are they sending me there? This is my third year here (Daytona),'" Petrick said. "When it comes down to it, you really just need to throw the ball, do what you need to do, and not worry about where you're at.
"I was a little upset, but I didn't have the best Spring Training," recalled Petrick. "I had a couple of walks in there and I wasn't throwing strikes. I was still throwing hard, though. My first week in Daytona, I had the same thing kind of happen. I wasn't throwing very good, but (then) something clicked."
Petrick also said that he is not willing to completely rule out a return to starting one day. Having started throughout most of his career, he says it is something a pitcher such as himself never completely forgets about.
"I really think about starting again," Petrick said. "I think my arm could hold up more as a starter because I know the routine and what I need to do to come back every five days. I think starting is always the way to go, but whatever I can do ... I'll come out of the bullpen again next year if they need me."