Justin Smoak played his first big league game in Fenway Park on Friday night, but it was not his first trip to the historic ballpark. In fact, the 24-year-old’s first visit to the home of the Red Sox had dramatic implications for both him and the club.

In 2005, Smoak was a tantalizing high school prospect. The 6-foot-4 switch-hitting first baseman showed significant power potential at Stratford High School in Charleston, S.C. He was a two-time state Player of the Year and a consensus prep All-American in a senior year in which he hit .558 with 18 homers.

Smoak had a strong commitment to the University of South Carolina. He represented a signability question entering the draft.

He hadn’t ruled out turning pro, but it would have taken a significant financial commitment to convince him to do so. As such, the Sox needed to scout him extensively to determine if he was worth the commitment.

“Coming out of high school, I wanted to go to college. It was going to take a lot for me to miss out on college. I think that teams knew that,” said Smoak. “It was a good bit. It was first-round money.”

The Red Sox scouted Stratford High extensively in the spring leading up to the 2005 draft, watching both Smoak and teammate Reese Havens (selected by the Mets in the first round of the ’08 draft) on several occasions and sending several different scouts and front office members to watch them play. The process was anything but frivolous.

“[The Red Sox] actually came down that year to Charleston, to South Carolina, to watch me and [Havens] play,” Smoak said in the Mariners clubhouse prior to Friday’s game. “[Sox GM Theo Epstein] came down to watch us play. It was cool. Growing up in Charleston, you don’t think about a general manager coming down to watch you play baseball. It was pretty cool. For them to bring Theo down definitely means something.”

So, too, did the fact that the Sox wanted both Smoak and Havens to take part in a pre-draft workout at Fenway Park that year. The ensemble of talent that day struck the Sox as tremendous, and it seems even more so with the benefit of hindsight.

In addition to Smoak and Havens, other amateurs at Fenway that day included current Pirates slugger Pedro Alvarez (whom the Sox drafted in 2005 but failed to sign), Cardinals center fielder Colby Rasmus, Mets outfield prospect Fernando Martinez and Orioles outfielder Nolan Reimold, among others.

For Smoak, the opportunity was thrilling.

“It was awesome,” he recalled. “Being 18 years old, being able to hit at Fenway Park, that was a dream come true for me.”

But the idea of being in Fenway Park proved more enticing than Smoak’s actual performance that day.

“I think I did so-so,” he said. “I was a little nervous. I think I hit a few balls off the Monster, but I don’t think I hit one out of here.”

Smoak’s performance was a disappointment to some in the Sox organization. Given what he sought as a bonus, that day – in which the ball simply didn’t come off the bat well – served as something of a deterrent.

Ultimately, based in part on Smoak’s performance at that Fenway workout, as well as due to the power hitter's commitment to South Carolina and cost of signing him, the decision was made that the Sox wouldn’t take the high school power hitter. The Sox had 18 picks in the first 15 rounds, but left Smoak on the board. It wasn’t until the 491st pick of the draft that the A’s selected him in the 16th round.

Smoak could not reach an agreement with the A’s (thus sparing the Coliseum from piles upon piles of “Smoakland” signs) and instead fulfilled his commitment to play for South Carolina. It didn’t take long for the Sox to regret their failure to draft him.

As a freshman, Smoak launched 17 homers for the Gamecocks, emerging as a force in SEC play. Following the season, he played in the Cape League, earning MVP honors.

During that summer with Cotuit, Smoak had occasion to think about what might have been with the Sox.

“It would have been nice,” said Smoak. “I got to come up after my freshman year of college and play on the Cape. Playing on the Cape, you watch the Red Sox every night on TV. When I was there, I became a fan of them, watching everyday.”

But the Sox would not have another shot at him. When he was next draft eligible, he was tabbed with the 11th overall pick in the 2008 draft by the Rangers. With Texas, he quickly emerged as one of the best power-hitting prospects in the minors, reaching the majors last season, less than two years after being drafted.

Though he struggled at the highest level, his potential remained obvious. As such, he became the prospect centerpiece of a deal that sent left-hander Cliff Lee from the Rangers to the Mariners last July.

Initially, Smoak struggled with his new club. He hit just .159 with a .439 OPS in his first 16 games with the Mariners, resulting in a trip to Triple-A.

“Last year, I was trying to do too much,” Smoak acknowledged. “Of course the fans think you’ve got to prove something right away, which is something I didn’t do. But then later, at the end of the year last year, I got back to what I was capable of doing, and I’m trying to carry that into this year.”

He has done just that. Smoak rejoined the Mariners for the last couple weeks of 2010, hitting .340 with a .421 OBP, .580 slugging mark and 1.001 OPS. This year, after going 1-for-4 with a walk and a two-run single against the Sox on Friday, he is hitting .300/.412/.557/.969 with four homers and 17 RBI.

It is that sort of performance that helped alter how the Sox approach the draft starting in 2006.

Frustrated by missing out on a chance to add either Smoak or Alvarez to their prospect pool in ’05, the team became more aggressive in scouting and signing high-ceiling high school players in 2006, when it spent liberally on such players as Ryan Kalish (9th round) and Lars Anderson (18th) in the middle rounds of the draft.

That approach has had its fair share of successes, whether with Kalish, Anthony Rizzo (now in the Padres system after being dealt in the Adrian Gonzalez trade) or others who are still at relatively early stages of their pro careers.

All the same, the return of Smoak to Fenway will no doubt leave some members of the organization to imagine play the “what if” game, daydreaming about the idea that Smoak could have impacted the organization through his own performance or as a trade chip to acquire someone like Lee. Even now, people involved with the '05 draft for the Sox will be asked how much the team offered Smoak. And when the question comes up, it is with a sense of some regret that the story of the decision not to draft the promising Mariners first baseman ends up being retold.