Luis Castillo says he's happy for Shawne Merriman. Happy for the success he's enjoyed, happy for the recognition he's received and happy the two rookies will be together on the Chargers defense for the next several seasons. But as Merriman is honored with a Pro Bowl berth and mentioned as a strong candidate for NFL Defensive Rookie of the Year, there's something else Castillo would like noted. "I've done a little bit, too," Castillo said. Actually, the Chargers' "other" first-round draft choice – Castillo was the 28th overall choice, Merriman the 12th – has done more than a little bit. As his first season comes to a close with tomorrow's game against Denver, Castillo is doing what a rookie should be doing – playing his best football of the season. "The last three (games) have probably been my best three of the season so far," said Castillo, who has started every game but the season opener at left defensive end. Not that tackles are the sole measurement of a defensive end's play, especially in the Chargers' 3-4 defense, but after making 28 tackles in the first 12 games, Castillo has been credited with 17 in the last three, including eight last week at Kansas City. He also had a huge fourth-quarter sack of Peyton Manning that helped the Chargers upset Indianapolis. Said Castillo: "To know you could go out there and make a big impact in a game and have (13) tackles the last two weeks and get to the quarterback and have pressures and do all the little things right and have my teammates recognize that . . . A lot of this game is confidence, and when you hear your teammates say, 'Wow, you played a great game,' that just gives you the confidence to go out there and do even better." Rare this season has been the opposing coach who mentioned Merriman's accomplishments without also including Castillo. Kansas City's Dick Vermeil called him one of the best defensive linemen to enter the league in the last several years. "A terrific young player who's developed far quicker than I would have imagined," Chargers coach Marty Schottenheimer said this week. "The thing I find remarkable is that, probably other than quarterback, that is the most difficult position to make a transition from college football to pro football. "He has really played extremely well for us over the past five or six ballgames, and the last three in particular." What really has Castillo excited is that he's just beginning. Only 22, he conceded he could use some rest after the 20-game season (including exhibitions), but at the same time, he can't wait for season No. 2. "About 4-5 weeks ago I remember saying I'm not looking past this year at all, and it's not saying I want this year to be over so I can go ahead and get into the offseason, but I look at how much I've improved," Castillo said. In watching film recently from the Chargers' first games against Denver (Week 2) and Kansas City (Week 8), Castillo said he hardly recognized himself. He even used the word "terrible" to describe his play from about 10 weeks ago. Was he really that bad? "By the standard that he is now setting, I wouldn't call it terrible," Schottenheimer said, "but it was certainly well below an acceptable barometer." Said Castillo: "I don't know why I was starting. And to see myself be able to do the things that I can now and have the three best games of the season, probably, the last three weeks, it's something where I can't wait for the opportunity to step back on that field next year. "I know I could do so much better. I'm encouraged. I know I can be a great player in this league. I have that confidence now." Castillo said there's no one area he wants to work on; he talked about improving "the little details." Added Castillo: "I'm a perfectionist when it comes to being on that field. I want every step, I want my hand placement, I want everything I do to be exact. "I'm looking forward to it so much because I know I can be so much better next year. And I haven't exactly been terrible this year." Neither, of course, has Merriman. And there's only one thing about his fellow rookie's season that has Castillo bothered. "I'm a little mad at him because he's not going to my party in the Dominican Republic now because it's Pro Bowl weekend," Castillo said, smiling. "But I've enjoyed watching him do the things he does and it just helps boost (the team)."