World Series since 2003. Soon, in many warm-weather regions, baseball came to be considered a major sport, approaching the level of football and basketball. And even non-warm weather schools started to recognize baseball's potential and began to put considerably more emphasis on it. Nebraska, Notre Dame, and Oregon State are three notable examples of cold (or rainy) weather schools with very successful programs. The first two made the College World Series when warm-weather schools placed major emphasis on baseball as well as had the advantage of playing earlier and more games because of favorable climates. Oregon State won back-to-back national championships in 2006 and 2007; at that time, arch rival Oregon had been without baseball for a quarter-century, having dropped its program in 1981. Many credit the Beavers' success as a primary factor in the University of Oregon's later decision to revive baseball in 2009. Before the Hubert H. Humphrey Metrodome was demolished in early 2014, Minnesota took advantage of it to play the majority of their games, including hosting a prestigious preseason tournament. With the 2010 departure of the MLB Minnesota Twins for the new Target Field, the school hoped to use the Metrodome for future Big Ten tournaments and bids on the NCAA tournament. Along with that, many smaller conferences (not in Division I) played games at the Metrodome during February in order to keep up with schools in warm-weather locations. While the Metrodome's replacement, U.S. Bank Stadium, was designed mainly for the NFL's Minnesota Vikings, it has movable seating banks that allow it to be configured for baseball. For 2008 and succeeding seasons, the NCAA mandated the first ever start date for Division I baseball, thirteen weeks before the selection of the NCAA tournament field, which takes place on Memorial Day. Collegiate rules The rules of college baseball are similar to the Official Baseball Rules. Exceptions include the following: The bat may be made of wood, or a composite material that meets NCAA standards. Since the 2011 season, composite bats have been required to pass the "Bat-Ball Coefficient of Restitution" (BBCOR) test. The designated hitter rule is used. In addition, a player may serve as both pitcher and DH at the same time and may remain in one position when removed in the other. One or both ends of a doubleheader are sometimes seven innings in length. However, the NCAA has recently tightened the interpretation of what