THE 2015 LAMAR HUNT U.S. OPEN CUP has featured terrific drama and some very impressive storylines so far. If you're not following the tournament, quite frankly, you’re missing out.

The early rounds have continued with the regional format and that has invigorated some local rivalries. There have been some intense games and some very interesting results.

Here are some thoughts on the first four rounds and what to expect as the fifth round (Round of 16) gets underway on June 30.

NASL teams are struggling

If North American Soccer League officials hoped to make a statement in this edition of the Open Cup, well, they can't be in a good mood right now.

In the third round, which was held on May 27, third division USL teams wiped out second-division NASL squads. In fact, the USL went a perfect 7-0 against the NASL and on Tuesday night NASL's Atlanta Silverbacks fell to the New York Red Bulls 3-0.

The only saving grace? The New York Cosmos' narrow shootout victory over New York City FC on Wednesday night.

USL's sweep is particularly interesting given that USL has applied to the U.S. Soccer Federation for second division status. While there can be two second divisions in the United States, USL seems eager to use this tournament, and its affiliation with Major League Soccer, to gain a stronger foothold on the American soccer landscape and a perfect record against the current second division NASL gives the league a boost of momentum.

The East River Derby

Billed as the East River Derby, the Cosmos’ matchup against New York City FC was quite a spectacle. Cosmos fans have had a chip on their shoulders for quite some time and many of them are very outspoken in their disapproval of MLS and its policies. Meanwhile, NYCFC fans showed up in great numbers at the Cosmos’ home on Long Island to voice support for their team.

The result was a wildly entertaining game that featured end-to-end action. NYCFC roared out to a 2-0 lead on two goals from Ghanaian forward Kwadwo Poku—who has emerged as one of the more exciting players in MLS. His first goal was a bicycle. His second should have been called offside but he did well to finish it.

The Cosmos found a way to fight back and equalized late and force extra time. NYCFC missed a chance to win after missing a penalty in the first stanza of extra time. In the shootout, Cosmos keeper Jimmy Maurer came up with a series of big saves for an improbable victory.

Cosmos fans were quick to celebrate the victory as a vindication that their club is on their way to becoming a giant club in the United States despite not playing in MLS. Conventional wisdom, however, suggests that this win merely helped the NASL avoid a disastrous 0-9 record against MLS and USL opponents.

Celebrating the fact that the only success the NASL had in this tournament came when its best team was able to defeat a struggling, less-than-full strength MLS expansion team only by the slimmest of margins, at home, seems about as appropriate as celebrating a D- on a report card

MLS teams stepping it up

MLS teams have long been criticized for not taking the tournament seriously. The U.S. Open Cup is more than a century old and is a legitimate cup competition. But MLS teams have often used the tournament as a chance to play reserve players. In one particularly embarrassing moment in 2011, New York Red Bulls head coach Hans Backe didn’t even travel with the team for an Open Cup matchup against Chicago. Instead he had his assistants coach the game and sent reserve team players.

This year seems to be a vast departure for all MLS teams. Many of the league’s top stars all played and the Red Bulls took a sharp turn from their organization’s history in the tournament and played a full strength squad in its 3-0 win over Atlanta.

Did MLS Commissioner Don Garber send a memo around? Perhaps. On Tuesday nine MLS teams advanced to the fifth round. Seattle was the only MLS team to lose on Tuesday but it lost to MLS rival Portland.

MLS teams delivered Wednesday as well: Orlando, Los Angeles, Columbus, D.C. United, and Houston all advanced. Only New England and New York City crashed out.

Fourteen of the 16 remaining teams are in MLS. The Cosmos and the Charlotte Independence of the USL are the only two lower division teams remaining.

Round of 16 Draw

The U.S. Open Round of 16 draw took place on Thursday morning and once again, the regional pots were used to determine the matchups. The marquee matchup will be the New York Derby featuring the Red Bulls and the Cosmos at Red Bull Arena.

Here's a look at the quarterfinal matchups (home team listed first).

EAST 

New York Red Bulls – New York Cosmos
Philadelphia Union – DC United

SOUTH

Chicago Fire – Charlotte Independence
Orlando City – Columbus Crew

CENTRAL

Sporting Kansas City – FC Dallas
Houston Dynamo – Colorado Rapids

WEST

Real Salt Lake – Portland Timbers
San Jose Earthquakes – Los Angeles Galaxy

Brian Sciaretta is an American Soccer Now columnist and an ASN 100 panelist. Follow him on Twitter.