When Philadelphia and Houston meet at BBVA Compass Stadium on Saturday (7:30 p.m., NBC Sports), it will be the ninth all-time meeting between the Eastern Conference rivals.
In less than three years, the Union have already squared off against the Dynamo six times in regular season play, and twice in the MLS Cup playoffs.
In franchise history, only D.C. United has played more games against Philadelphia.
The all-time series between the Dynamo and Union is split right down the middle: three wins, three losses, and two draws. Only three times in this series has the home team won. Philadelphia has two wins at Robertson Stadium, but did not defeat the Dynamo at PPL Park until last month.
Here's a brief history of the previous eight matchups between Philadelphia and Houston:
May 29, 2010: Union 3, Houston 2 (Robertson Stadium)
A defining moment in Union history.
This was Philadelphia's first road win, a come-from-behind victory in enemy territory.
Shea Salinas opened the scoring in the 39th minute with a brilliant run down the right flank that ended with a tight-angle flick past goalkeeper Pat Onstad. It was voted MLS Goal of the Week and remains one of the most impressive goals ever scored by a Union player.
Houston looked to have wrapped up the win with back-to-back set piece goals in the second half, but Sebastien Le Toux equalized in the 69th minute before assisting on Danny Mwanga's dramatic game-winning goal in the 93rd.
Oct. 2, 2010: Union 1, Houston 1 (PPL Park)
The first matchup between Houston and Philadelphia at PPL Park.
Andre Hainault tallied for the Dynamo in the 12th minute, after former Union keeper Chris Seitz knocked down a Brad Davis shot from inside the box. The ball fell to the Houston defender, who hit a rocket into the back of the net.
Philadelphia earned the equalizer on a brilliant goal in the 40th minute. Roger Torres was able to separate from Davis and play in a beautiful cross behind the Dynamo backline. Le Toux beat the offside trap, controlled with his left foot, and used his second touch to slide the ball underneath Tally Hall's far post. That strike was nominated for MLS Goal of the Week.
March 19, 2011: Union 1, Houston 0 (Robertson Stadium)
The match marked former Union captain Danny Califf's first and only goal in Union colors, but it was good enough to give the Union a scrappy road win in the 2011 season opener.
It began with a Sheanon Williams throw-in, which Le Toux controlled and hit off the crossbar. Califf was there to bungle home the fourth minute goal, and the defense shutout the Dynamo for the remaining 86 minutes.
Aug. 6, 2011: Union 1, Houston 1 (PPL Park)
A disappointing finish for the Union, who conceded late after blowing a chance to go up 2-0 at home.
Jack McInerney started the scoring with a nice right-footed flick past Tally Hall in the 15th minute. A snake-bitten Le Toux had a chance to double the lead late, but hit the post in a one-on-one situation after Stefani Miglioranzi's through-ball opened up the Houston defense.
Just one minute after that miss, Geoff Cameron found space at the edge of the box, beat a defender, and hit a low drive past Faryd Mondragon.
Oct. 30, 2011: Houston 2, Union 1 (PPL Park)
The game that most fans have tried their hardest to forget.
Former manager Peter Nowak deployed a five-man defense in the Union's first-ever playoff game, opting for defensive tactics at PPL Park.
The Union's Achilles heel, set piece defense, was exploited in the fifth minute of the game. Brad Davis found Hainault in the box, and Houston scored their third set-piece goal against Philadelphia in five total games.
Le Toux equalized just minutes later, but Calen Carr's 30th minute goal proved to be the game winner.
It was Houston's first win against Philadelphia, and only the second loss for the Union at PPL Park in 2011.
Nov. 3, 2011: Houston 1, Union 0 (Robertson Stadium)
The second leg of the playoff series was just as forgettable as the first.
Nowak scrapped the five-man defense, but the Union offense was mostly ineffective with Le Toux playing on the right flank.
Davis was the nemesis again, hitting a pinpoint cross in first-half stoppage time that was headed home by Ching.
Philadelphia failed to score, and Houston won the semifinal series 3-1 on aggregate.
June 30, 2012: Houston 2, Union 1 (BBVA Compass Stadium)
Philadelphia's first trip to the brand new BBVA Compass Stadium ended with a third straight loss to the Dynamo.
Davis scored in the first half, a poor first half for the Union after back-to-back home wins against Kansas City and Harrisburg.
Keon Daniel scored a great goal in the second half to equalize at 1-1. But Houston took home three points after Ching converted an 83rd minute penalty kick. A controversial call, Gabriel Farfan was judged to have shouldered Ching inside the box. The Dynamo forward went to ground and referee Fotis Bazakos pointed to the spot.
Sept, 23, 2012: Union 3, Houston 1 (PPL Park)
Revenge for the Union, who simultaneously snapped an eight-game winless streak, and a three-game losing streak against Houston.
The Union offense came to life in this one, breaking a streak of 747 minutes in which a Union striker had not scored a goal.
The win evened the all-time series against the Dynamo at 3-3-2.
Contact Kevin Kinkead at email@example.com. Follow Kevin on Twitter @PhilUnionKevinK