Preseason All-American teams are similar to preseason top-25 rankings in that neither guarantees succe s. However, these are not pointle s, as the lists can help college football fans get ready for the upcoming season by letting them know the best players and teams to look forward to this fall.And after a few months without football, I think fans are ready to ingest any available information to get ready for the upcoming season.So, here are my early favorites to capture top FBS All-American honors at the end of the 2015 season, as well as others likely to be in the hunt for the top spots if they can step up their games this fall. I'll be taking a look at each position, continuing today with defensive linemen.Defensive EndsEarly FavoritesJoey Bosa, Ohio State: Bosa was a finalist for multiple national awards as a sophomore (21 tackles for lo s, 13.5 sacks) but he'll take a few home after this season. The Big Ten's 2014 Defensive Player of the Year is already being called a mini- (at 6-foot-6, 275 pounds, mind you) because he lines up inside and outside and has the length, strength, and agility to make plays reminiscent of those made by the reigning NFL Defensive Player of the Year.Shawn Oakman, Baylor: We're all in awe of the physical attributes that this 6-8, 280-pound, chiseled athlete po se ses. When playing with leverage, Oakman can take any left tackle in the country straight into the quarterback. Oakman's 19.5 tackles for lo s and 11 sacks earned him first-team All-Big 12 and third-team All-America honors last season. He'll likely be a first-team All-America Mario Manningham Jersey selection this season if he dominates as regularly as his physique should allow.Others in the huntDerek Barnett, Tenne see: The Tenne see native made a great first impre sion as a true freshman in 2014. Barnett (6-3, 258) made the most tackles for lo s of any Volunteer since 2000 (20.5) and recorded 10 sacks, utilizing a nice combination of strength, get-off, and an innate ability to get under the pads of his man to shorten the corner.Shilique Calhoun, Michigan State: The two-time first-team All-Big Ten pick surprised some by returning to school for his senior year after accumulating 26.5 tackles for lo s and 15.5 sacks over the last two seasons. Look for double-digit sacks from Calhoun (6-5, 250) in his last year in Lansing.Myles Garrett, Texas A&M: Garrett's true freshman campaign already puts him among the best in the country at his position. The second-team All-SEC pick (14 tackles for lo s, 11.5 sacks) has good size (6-5, 255). His natural bend gives him a chance to get around offensive tackles in a hurry as he pursues the quarterback. The sky is the limit for Garrett, and he'll likely be a fingertip away from the clouds in 2015.Emmanuel Ogbah, Oklahoma State: Ogbah, a native of Lagos, Nigeria, made an instant impact as a redshirt freshman in 2013, recording four sacks. In 2014, he rode an accelerated learning curve into a Big 12 Defensive Lineman of the Year season (17 tackles for lo s, 11 sacks). Obgah is not the swiftest edge rusher in the country, but will once again rack up big numbers because of his strength at the point of attack against the run as well as his hustle to the ball.A'Shawn Robinson, Alabama: In the Tide's 3-4 alignment, Robinson lines up in the five-technique defensive end position, even though he's 6-4, 312 pounds. He can play the position at that size because of his tremendous athleticism. However, he can hold up at nose tackle and has the ability to collapse the pocket from anywhere on the line, which gives him a chance to earn All-America honors.Defensive TacklesEarly FavoritesMaliek Collins, Nebraska: Any offensive line that doesn't double-team Collins should be prepared to pay the price. He earned second-team All-Big Ten accolades as a sophomore (14 tackles for lo s, 4.5 sacks) by out-quicking guards off the snap, ripping them aside with