[MLS IMPORT WATCH] Perhaps even more important than the imports brought in for the start of the new MLS season are those imports who arrive in mid-season -- players made available from the larger pool of available players following the end of their season in Europe and South America. With their first full preseason under their belt, these imports are among the key players to watch in MLS. For our first MLS Import Watch of the 2013 campaign, here's a look at five summer imports (throwing in Ricardo Clark, back from Europe) who played key roles in opening day wins ...

RICARDO CLARK (Houston). After struggling in Germany and sinking in Norway, Clark welcomed the return to his old MLS club. And he opened the season with a commanding performance in midfield, the kind that made him a national team regular under Bob Bradley. His run set up the (dubious) penalty Brad Davis failed to convert, but he finished off the 2-0 win over D.C. United with a blast to the near post.

FEDERICO HIGUAIN (Columbus). The brother of Real Madrid star Gonzalo Higuain arrived from Colon in mid-season and did well enough in 13 games -- five goals and seven assists -- to win the MLS Newcomer of the Year award. He began where he left off with the first goal -- a blast from 25 yards -- in the Crew's 3-0 win at Chivas USA.

ALESSANDRO NESTA (Montreal). The only former World Cup champion currently in MLS besides New York's Thierry Henry, Nesta arrived last summer from AC Milan after 19 seasons in Italy. He was limited to only eight games, however, and said in the offseason he might retire after the 2013 season. Nesta turns 37 March 19 but showed in the Impact's opener at Seattle that he still has something left in the tank. He played a key role in shutting down the Sounders for a well-deserved 1-0 win.

ANDY O'BRIEN (Vancouver). The Irish international arrived in Vancouver last August after 16 seasons in England, and his presence on the Whitecaps' backline took on even more important when Jay DeMerit went down after eight minutes with a potentially season-ending injury in the opener against Toronto FC. His long ball triggered the sequence that led to Gershon Koffie's goal in the 60th minute, lifting Vancouver to a 1-0 victory.

ORIOL ROSELL (Sporting KC). There aren't many players who can say thet played youth soccer at Real Madrid and Barcelona, but that's what Rosell did. He never cracked the first team at Barca, so he moved to Kansas City late in the 2012 season. He played just 127 minutes during the regular season but showed enough for SKC to ship Brazilian veteran Julio Cesar off to Toronto. Rosell started against Philadelphia and scored the winning goal with a header in the 3-1 win at PPL Park.