As a three-time Stanley Cup-winning franchise, the Pittsburgh Penguins have had their share of great teams and great players.

While some of these players, such as Mario Lemieux and Sidney Crosby, have come by way of the draft, others have come by way of trades.  

With seven players entering free agency and, with prominent players such as Kris Letang and Marc-Andre Fleury being mentioned in trade rumors, this offseason figures to be an eventful one in Pittsburgh.

As Penguins general manager Ray Shero looks to make upgrades to the Pens roster for next year, whether through free agency or trades, let's look back at the five best trades in Pittsburgh Penguins history.

No. 5: The Penguins Rebuild Their Blue Line

Sometimes, trades are not appreciated at the time they are made and require a certain amount of hindsight in order to see their value.

That certainly applies in the case of the the trade made in December 1990 that brought defensemen Larry Murphy and Peter Taglianetti to Pittsburgh from Minnesota in exchange for defensemen Chris Dahlquist and Jim Johnson.

Entering the 1990-1991 season, the Pens were a team with a high-powered offense but one that lacked mobile and offensively minded defensemen capable of skating or passing the puck out of the zone.  This trade changed that.

In Murphy, the Pens gained a smooth-skating defenseman who could man the point on the power play and control the tempo of the game with his play-making ability.

In Taglianetti, the Pens added a smart yet physical defense partner for Paul Coffey who was then able to become more active in the offensive zone and fully showcase his Hall of Fame talents.  

While Craig Patrick's other moves often overshadow this deal, it's hard to imagine the Penguins winning two Stanley Cups without the trade that brought Murphy and Taglianetti to Pittsburgh.

No. 4: Joe Mullen Brings Stanley Cup Pedigree to the Penguins

In the summer of 1990, the Pittsburgh Penguins were at a crossroads.

Having missed the playoffs despite the MVP-calibre play of Mario Lemieux, the Pens faced a dilemma.  Were they going to continue to rely solely on drafting and developing players within the organization or was it time to trade for established players in order to build a Stanley Cup contender?

At the 1990 NHL Entry Draft, Pens GM Craig Patrick opted for the latter and, on the advice of head coach Bob Johnson, traded a second-round pick to the Calgary Flames for forward Joe Mullen.

Johnson had coached Mullen in Calgary and believed that he still could be a premier goal scorer.  Flames management believed that, at age 33, Mullen's best years were behind him even though he had scored 87 goals during the previous two seasons.

Fortunately for the Penguins, Mullen's play vindicated the faith that they showed in him as he would average 30 goals per season over the next three years and helped lead the Pens to back-to-back Stanley Cups in 1991 and 1992.

While Joe Mullen would go to score 153 goals for the Penguins and finish his Hall of Fame career in Pittsburgh, the player that the Flames drafted with the second-round pick they acquired in the trade, defenseman Nicolas Perreault, never played in the NHL.

No. 3: Draft Day Deal Lands Marc-Andre Fleury

After years of dealing with financial uncertainty and having been forced to sell off his best players, Pittsburgh Penguins GM Craig Patrick arrived at the 2003 NHL Entry Draft looking to make a bold move and begin the process of rebuilding a beleaguered Penguins franchise.

When the Florida Panthers made it known that they were willing to deal the first-overall pick, Patrick moved quickly to acquire it along with the Panthers' third-round pick in exchange for the third-overall pick, the Pens' second-round pick and forward Mikael Samuelsson.

With the trade complete, the Pens then drafted goaltender Marc-Andre Fleury of the Quebec Major Junior Hockey League making him only the third goaltender to be selected with the first-overall pick after Michel Plasse in 1968 and Rick DiPietro in 2000.  With a strong showing in training camp, Fleury earned a spot with the Pens making him the first goaltender since Tom Barrasso, who led the Pens to back-to-back Stanley Cups in 1991 and 1992, to go straight to the NHL without a stop in the minors.

As the youngest goaltender in NHL history (three months younger than the second-youngest, Rick DiPietro when he started for the New York Islanders), Fleury made an immediate impact by earning Rookie of the Month honors in October 2003 and showed that he could be the franchise goaltender that Patrick envisioned when he made the trade.

By the end of his second season, Fleury had emerged as the Penguins' starting goaltender and helped lead them to a Stanley Cup in 2009.

No 2. Trade for Marian Hossa Leads the Pens to Stanley Cup Finals

By the spring of 2008, the Pittsburgh Penguins were considered by many to be an up-and-coming-team but not a serious contender for the Stanley Cup.

That view changed when Pens GM Ray Shero landed the biggest name on the trade market, forward Marian Hossa, who, along with Pascal Dupuis, was acquired from the Atlanta Thrashers in exchange for forwards Erik Christensen, Colby Armstrong and Angelo Esposito along with the Pens' first-round pick in the 2008 draft.

With the addition of Hossa, the Pens had finally acquired an all-star winger to play alongside Sidney Crosby and had become a force to be reckoned with in the postseason.  During the 2008 Stanley Cup playoffs, Hossa led the Pens in scoring and tallied 12 goals including the series-clinching goal in overtime of Game 5 against the New York Rangers which propelled the Pens to the Eastern Conference Finals for the first time since 2001.

In Dupuis, the Pens gained a fast-skating and hard-working player who has become a fixture on the top line.  This past season, he scored 20 goals in just 48 games and figures to be the Pens' top priority in free agency.

Although the Pens would fall short to Detroit in the Stanley Cup Finals, the acquisition of Hossa and Pascal Dupuis proved to be an important step in the development of an inexperienced Pens team.

While many fans still hold a grudge against Hossa for rejecting the Pens' contract offer and jumping to the Red Wings later that year, it should not forgotten that the trade that brought him to Pittsburgh made the Penguins instant contenders and paved the way for them to win the Stanley Cup the following season.

No. 1: Craig Patrick's Blockbuster Makes the Penguins Stanley Cup Champions

While every general manager dreams of making a trade that turns his team into a Stanley Cup Champion, Penguins GM Craig Patrick made that dream a reality.

By the spring of 1991, the Penguins were a high-scoring team with a .500 record.  Although the Pens boasted one of the NHL's top offenses led by Mario Lemieux, they needed to improve defensively to make a run at the Stanley Cup. 

To address this need, Patrick pulled the trigger on a blockbuster deal that sent high-scoring center John Cullen, forward Jeff Parker and defenseman Zarley Zalapski to the Hartford Whalers in exchange for center Ron Francis and defensemen Ulf Samuelsson and Grant Jennings.

For the Pens, the trade paid immediate dividends as they finished the season with a mark of 9–3–2 and won their first ever Patrick Division championship.

With Ron Francis' strong two-way play and with the toughness provided by Ulf Samuelsson and Grant Jennings, the Pens emerged as a well-rounded team and would win back-to-back Stanley Cups in 1991 and 1992.  

While the Pens may have won a Stanley Cup eventually even without this deal by Craig Patrick, there's no denying that this blockbuster trade with the Hartford Whalers led directly to back-to-back Stanley Cups and was the biggest trade in Pittsburgh Penguins history.