If you asked fans of Major League Soccer at the beginning of the season who they thought would lead the Eastern and Western Conferences at the halfway mark, no one would've answered with the Philadelphia Union and Colorado Rapids. 

Both clubs have taken different approaches to reach the top of their respective conferences, but each way has been effective. Philadelphia revamped its roster through the MLS SuperDraft and with a few young signings, while Colorado has relied on league veterans and a United States men's national team star to navigate the treacherous waters of the West. 

Philadelphia was aggressive at the top of the 2016 MLS SuperDraft as it attempted to build depth at every position, a goal stated by technical director Earnie Stewart when he took over after the end of the 2015 regular season. 

The Union used two trades and their original draft pick to select Georgetown University defenders Joshua Yaro and Keegan Rosenberry as well as Creighton University forward Fabian Herbers.

Rosenberry has seen the most playing time of the trio and found himself in the spotlight for a stretch of matches in May after he shut down Robbie Keane, Giovani dos Santos, Didier Drogba and Ignacio Piatti in one-on-one situations. The No. 3 overall pick is a front-runner for Rookie of the Year and is currently fourth in All-Star voting. 

One of the Union's draft picks from two years ago is also thriving after a tumultuous situation at the goalkeeper position. The old regime in Philadelphia tarnished the development of Andre Blake by bringing in Algeria international Rais MBolhi, who turned into one of the worst acquisitions in the history of MLS. In his first year as a full starter, the 25-year-old Blake has made 47 saves and earned six of the club's seven wins.

The Union have also benefited from their improved play at their home stadium. Jim Curtin's side didn't lose at Talen Energy Stadium until June 25 against the Vancouver Whitecaps. Philadelphia holds a 6-1-2 mark at home and has earned an additional six points on the road, including an impressive spell at the end of May in which it took a point from Orlando City and the Rapids in a three-day stretch. 

Some shrewd personnel moves have also helped Stewart and Curtin form their club's identity. Forward C.J. Sapong, who missed a chunk of 2015 due to a few circumstances, has become the physical presence they need up top, while Tranquillo Barnetta and offseason acquisition Chris Pontius have combined well with mainstay Sebastien Le Toux. 

But the Union are currently in the middle of a three-game skid caused by the sudden departure of central midfielder Vincent Nogueira, who mutually parted ways with the club due to personal health reasons. Since the Frenchman, who was one of the most underrated players in MLS, left, the Union have given up three goals per game against New York City FC, Chicago and Vancouver. 

The Union will be in the market for a new defensive-minded midfielder during the summer transfer window, but for now they have to fix the issue with Barnetta and Dutchman Roland Alberg, who hasn't stopped scoring since he entered the lineup. 

Philadelphia's biggest concerns over the final four months of the season will be replacing Nogueira, holding firm in the back as its young set of defenders take on bigger challenges and fending off the established sides in the East that will surely make a run for the top spot. 

Over in Colorado, manager Pablo Mastroeni has produced one of the most amazing turnarounds in league history after finishing last in the West a year ago. Thanks to a league-high nine wins and a perfect home record, the Rapids lead the West and the Supporters' Shield standings with 32 points, six more than Philadelphia has atop the East. 

The Rapids have used a mixture of MLS castoffs, European signings and the surprising addition of Jermaine Jones to catch the West by storm. After losing goalkeeper Clint Irwin and center-back Drew Moor to Toronto FC in the offseason, many thought the Rapids would struggle on the defensive side of the pitch. 

Veteran Bobby Burling and second-year man Axel Sjoberg have formed one of the unlikeliest center-back pairings in the league and have led Colorado to the best defensive record in MLS. The Rapids have conceded on only 11 occasions in 2016. The next-best total belongs to Toronto FC and the LA Galaxy, who have both let in 18 strikes to date. 

The European flavor in attack has led to some surprising results as well, as Albania international Shkelzen Gashi and Republic of Ireland forward Kevin Doyle have been able to consistently produce chances alongside an unusual player in the No. 10 role. 

After he returned from his six-game suspension to start the season, Jones was pushed forward in the Colorado attack and produced results immediately. In his first appearance, the 34-year-old contributed a goal and an assist in a 2-1 win over the New York Red Bulls. The furious attacking pace of Jones led to two more tallies and an assist in the next three games. The Rapids earned 10 of a possible 12 points during that span.

But the most valuable additions made by the Rapids in 2016 have come from the Seattle Sounders. Midfielders Micheal Azira and Marco Pappa have been key assets to a midfield that doesn't get enough respect on a national level. Azira, who only played in 25 games in two seasons with Seattle, has been in the starting XI for each of Colorado's 16 league matches. The play of the 28-year-old in front of the back four is one of the key reasons for the club's superb defensive record. 

Winger Marco Pappa was always a solid contributor in Seattle, but his talents have taken on a new importance in a less talented attacking group. The Guatemala international made an instant impact with one goal and three assists in his first six matches. The 28-year-old recently returned from injury on June 22 and should return to his role as a consistent contributor once he regains full match fitness. 

Despite all the attention that the field players deserve for their achievements during the first half of the 2016 campaign, all eyes are on Colorado's goalkeeping situation at the moment. USMNT stalwart Tim Howard is set to replace 24-year-old Zac MacMath in the near future, despite the solid form of MacMath and Howard's lack of playing time at Everton and the USMNT since the start of the calendar year. 

Disrupting the chemistry of a back line that has conceded 11 times in 16 matches is something most clubs wouldn't do, but someone with Howard's resume doesn't become available that often. Getting off to a good start with Howard in net will be key, especially since the margin for error in the West is so slim.

The Rapids enter July with a one-point advantage on FC Dallas and a five-point lead on Real Salt Lake. In addition, perennial powers like the LA Galaxy, Portland Timbers and Sporting Kansas City are expected to discover more form in the second half of the season. 

Both Philadelphia and Colorado deserve all the praise they receive for reaching the middle part of the regular season atop their respective conferences, but in order to remain there at the end of October, they each need to fix one big ongoing issue and fend off the challenges from the other respected sides in their conferences. 

No one knows what will happen in the unpredictable league that is MLS, but if we've learned anything in the first four months of play, it's that Philadelphia and Colorado are here to stay. 

Joe Tansey covers MLS for Bleacher Report. You can follow him on Twitter, @JTansey90. 

All statistics obtained from MLSSoccer.com. 

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