Since Philadelphia Union joined Major League Soccer in 2010, no opponent has featured more prominently than I-95 rival D.C. United.
Sunday's matchup will be the 10th all-time meeting between the clubs, the continuation of a series that always seems to provide compelling storylines and drama both on and off the field.
The first seven matches against D.C. United were played at four different venues: Lincoln Financial Field, RFK Stadium, PPL Park, and the SoccerPlex in Boyds, MD. Five of the first seven games were decided by just one goal.
Sure enough, the all-time record is fairly even: three wins for Philadelphia, four wins for D.C. United, and two draws.
Last season, the clubs met four times, with three regular season games and a matchup in the U.S. Open Cup. This year, there are three scheduled league games with the future possibility of another Open Cup showdown.
1. April 10, 2010 – Philadelphia 3, D.C. United 2 (Lincoln Financial Field)
Goals: Le Toux 4', 40', 80' Quaranta 63', Moreno 70'
Philadelphia's first home game. Philadelphia's first goal. Philadelphia's first hat-trick.
Sebastien Le Toux stole the show with a three-goal performance that, two seasons later, still hasn't been matched.
The Frenchman struck in the fourth and 40th minutes to give the Union a 2-0 lead. That advantage was later squandered, after Santino Quaranta and Jaime Moreno both scored, the latter goal coming from a Chris Seitz gaffe inside the Union penalty area.
But Le Toux found the winner on an 80th minute free kick, after Dejan Jakovic was red carded for pulling down Alejandro Moreno on a breakaway.
Not a bad way to finish your hat trick.
Vice President Joe Biden joined some 35,000 soccer fans who filled up the entire lower bowl of the Eagles' stadium for the Union's hometown debut.
2. August 22, 2010 – D.C. 2 Philadelphia 0 (RFK Stadium)
Goals: Allsopp 22', 63'
This was a rainy, sloppy affair in the Nation's capital.
Interim head coach Ben Olsen had recently taken over for Curt Onalfo, and D.C. United was on a five-game losing streak.
Australian striker Danny Allsop scored a brace, and United won their first home game in nearly three months.
It was also D.C. United's first shutout of the entire season. United had entered the game with a record of 3-14-3.
A 17-year-old named Andy Najar impressed on the wings, drawing speculation as to whether he might devote his international future to Honduras, or the USA. He would eventually move on to join U.S. international Sacha Kljestan at Belgian powerhouse Anderlecht.
3. April 6, 2011 – D.C. 2 Philadelphia 2 (DC wins 4-2 on PKs, U.S. Open Cup at Maryland SoccerPlex)
Goals: Ruiz 18', Wolff 45', Woolard 111', Carroll 117'
Penalties: Le Toux (good), Pontius (good), McInerney (miss), Barklage (good), Torres (miss), Najar (good), Nakazawa (good), Boskovic (good)
Talk about a wild one.
This was an Open Cup game at the SoccerPlex in Boyds, Maryland.
Carlos Ruiz scored the opener 18 minutes in, but Josh Wolff found the equalizer before the end of the first half.
In the 87th minute, there was an altercation involving Carlos Valdes, and the Union center half was ejected after picking up his second yellow card. Daniel Woolard put D.C. ahead in the 111th minute, then Brian Carroll got the 10-man Union back to level terms in the 118th minute. Manager Peter Nowak was ejected for "excessive celebration", and the game went into penalty kicks.
Sebastien Le Toux and Chris Pontius both scored on their opening PKs, but Jack McInerney missed the net before Bill Hamid saved Roger Torres' attempt. D.C. United won 4-2 in the shootout and advanced to the next round of the tournament.
4. July 2, 2011 – D.C. United 2, Philadelphia 2 (RFK Stadium)
Goals: Wolff 44', Kitchen 49' (own goal), Najar 58', Ruiz 84'
This was the debut of Dwayne De Rosario in a United shirt.
"De Ro" assisted on the 44th minute opener, after he drew two Union defenders and played a square ball for Wolff to slot home.
Philadelphia leveled in the 49th minute, when Veljko Paunovic hit a cross that rookie Perry Kitchen awkwardly shanked into the net. The ball appeared to come off his shin.
After Najar's rocket shot beat Faryd Mondragon from beyond 35 yards, Philadelphia carved out a late game equalizer. Le Toux was able to play in Sheanon Williams, who got behind the defense and crossed for Carlos Ruiz. Pescadito's late goal earned the Union their first point at RFK Stadium.
5. September 29, 2011 – Philadelphia 3, D.C. United 2 (PPL Park)
Goals: Le Toux 4', 16' De Rosario 21', Najar 30', M. Farfan 57'
This was the first time D.C. United played at PPL Park.
The Union won 3-2 in an exciting game that was televised nationally on ESPN 2. The three points were absolutely critical in an Eastern Conference playoff race that had begun to tighten up towards the tail-end of the season.
Le Toux scored a brace, with both goals coming from direct balls over the top of Brandon McDonald and Ethan White. Philadelphia was playing in the successful 4-5-1 hybrid shape that included Paunovic in a combined midfield-forward role.
Just like the first meeting between these teams, D.C. United found a way to even the score at 2-2. De Rosario and Najar both netted goals for United to cancel out Le Toux's first-half pair.
But it was rookie Michael Farfan, who assisted on the second goal, that scored the game-winner. The midfielder took a pass from Torres, dribbled untouched to the top of the box, and slammed home a left footed shot from 20 yards out.
6. June 5, 2012 – Philadelphia 2, D.C. United 1 (U.S. Open Cup at Maryland SoccerPlex)
Goals: Wolff 45', Carroll 45', Hoppenot 93'
Philadelphia's first road win against D.C.
Just like the 2011 version at the SoccerPlex, this game also featured late drama and controversy.
Ironically enough, Brian Carroll scored his second goal in consecutive years against United at the SoccerPlex. And even more ironic – Josh Wolff equalized for D.C. United.
As Yogi Berra would say, it was like "deja vu all over again".
This game went into extra time for the second year in a row. Rookie Antoine Hoppenot scored the eventual winner in the 93rd minute.
After Zac MacMath's critical save on Hamdi Salihi, a brawl broke out on the United end of the field. Brandon McDonald was ejected, and Carlos Valdes was also ejected for the second time at the SoccerPlex.
It was an odd set of circumstances. Brian Carroll scored his second goal at the SoccerPlex, and Carlos Valdes was red carded at the same venue where he was tossed in 2011.
7. June 16, 2012 – D.C. United 1, Philadelphia 0 (PPL Park)
Goals: Pontius 78'
The beginning of the John Hackworth era, and a bit of revenge for D.C.
This game was played just 11 days after the Open Cup match in Boyds.
Philadelphia looked energized from the start, creating scoring chances but failing to get on the board.
The game was deadlocked until the 78th minute, when Valdes was yellow carded for a challenge on Chris Pontius. Replay showed that Valdes had gotten a touch on the ball, but referee Ricardo Salazar awarded United with a set piece. Branko Boskovic hit a brilliant free kick that was slotted home by Pontius at the far post.
8. August 19, 2012 – D.C. United 1, Philadelphia 1 (RFK Stadium)
Goals: Carroll 8', Okugo 71' (own goal)
Go figure, Brian Carroll scored again versus his former club, slotting home on the goal line after Carlos Valdes' found the ball in the box and hit a shot that deflected off of Perry Kitchen's noggin.
D.C.'s leveler was unfortunate, with Amobi Okugo accidentally heading a dangerous free kick into his own net. The Union defender had stooped low in anticipation of a re-direction, but the ball went untouched into the box and ended up going in at the far post.
The real drama began in the 85th minute, when Roger Torres brought down Chris Pontius inside the penalty area. De Rosario nailed the spot kick, but referee Mark Geiger called back the goal, ruling that Hamdi Salihi had encroached on the play.
Boskovic was red carded in a scuffle that broke out after the kick, then De Rosario blasted his retake over the bar.
But it didn't stop there.
Emiliano Dudar earned a straight red for a rash challenge on Antoine Hoppenot. That prompted a verbal response from Pontius against his own teammate.
Sheanon Williams was tossed just minutes later, receiving a second yellow on a challenge in which replay confirmed he had touched the ball before bringing down Pontius.
That cued a shoving match with Bill Hamid, (see above image) who came out of his goal to confront Williams.
The whistle eventually blew, and United's Chris Korb and Brandon McDonald exchanged words and a shove before walking off into the locker room.
9. September 20, 2012 – D.C. United 1, Philadelphia 0 (PPL Park)
Goals: Pajoy 67'
"He didn't do that for us, did he?" - Sheanon Williams' famous quote after former Union striker Lionard Pajoy scored the game winner at PPL Park.
Philadelphia earned the lion's share of possession and out-shot their rivals 14 to 7 on the evening. The Union were credited with 5 shots on target to D.C.'s 2, the visitors sorely missing injured playmaker De Rosario.
It was the second time in 2012 that United had walked away from PPL Park with 3 points.
Contact Union writer Kevin Kinkead at email@example.com