Tank Carradine repeatedly made one thing clear: his right knee has made a remarkable recovery from November reconstructive surgery and he expects no long-term problems that could derail his NFL career.The San Francisco 49ers selected the defensive end from Florida State with the 40th pick in the second round of the NFL draft Friday, and love the versatility he brings to their 3-4 defense to play several spots in various packages."My knee feels great. There's nothing wrong with my knee," Carradine said on a conference call. "There's no long-term things that I think will go wrong with my knee, because I'm healthy."San Francisco extensively reviewed the 23-year-old Carradine's medical records - he had surgery to repair a torn anterior cruciate ligament - at Stanford on Thursday.General manager Trent Baalke isn't overly concerned."We're very confident in what we know of his condition. Obviously, he was at the combine and our medical staff took a very close look at him," Baalke said. "The No. 1 thing with Tank is getting him healthy, getting him ready to play."The 49ers are counting on him emerging as a consistent contributor in short order. A talented pass-rusher from both sides of the line, Carradine could eventually shift to defensive end down the road if Justin Smith leaves the franchise - and he is heading into the final year of his contract.San Francisco quickly filled another big need Friday night, trading up to select Rice tight end Vance McDonald with the 55th selection. The NFC champions acquired the pick from the Green Bay Packers, giving up the 61st choice in the second round and a sixth-round pick at No. 173. San Francisco later pulled off another swap with the Packers to move up five spots and choose Auburn defensive end Corey Lemonier at 88th.The 49ers lost tight end Delanie Walker, Vernon Davis' backup, to the Titans last month in free agencyMcDonald was surprised to be chosen by the 49ers."I kind of just had the feeling it was going to be someone coming out of left field and grabbing me up, and that's pretty much what happened here," he said.Now, McDonald must prepare for quarterback Colin Kaepernick's zippy passes, or "fireballs" as he called them."It's awesome to know I'll be a part of it," he said of the offense.The agile Carradine, known for his quick-burst ability off the line, played right defensive end in college.49ers defensive line coach Jim Tomsula traveled to Carradine's hometown of Cincinnati last week to watch him hold a workout. They also enjoyed a productive get-to-know-you dinner."It was a great dinner. We talked about football, we talked about life as well," Carradine said. "He was able to get to know me as a person and a player and I was able to get to know him as a coach. I see myself fitting right in and come out there and learn from that defense."San Francisco pulled off a trade with Tennessee on Friday afternoon to give up the 34th choice and move down six slots, also acquiring the Titans' seventh-round choice at No. 216 and a third-round pick next year.A day after trading up to select free safety Eric Reid with the 18th pick, Baalke addressed another need on Day 2. The GM said Thursday he was prepared to make the pick at 34, or trade it if the NFC champions received the right offer.While Carradine hopes to participate in the team's rookie minicamp next month, he knows the doctors will make the final call - and he wants to make sure he is healthy to contribute right away as a rookie.Yet Carradine wasn't sure whether teams would shy away from him considering the knee issue."I was able to come back fast," he said. "I was hoping I would go in the second round and teams would take a chance on me in the second round."The 6-foot-4, 276-pound Carradine will add depth and fill voids to a unit following the departures of nose tackle Isaac Sopoaga and tackle Ricky Jean Francois in free agency. Carradine will join a rookie class in Silicon Valley that includes new free safety Eric Reid, the LSU defender taken 18th overall Thursday night.Reid was formally introduced Friday, and is looking forward to matching up with Packers quarterback Aaron Rodgers in Week 1 - along with traveling to London for the first time when San Francisco plays Jacksonville on Oct. 27 at Wembley Stadium."If I could pick off Aaron Rodgers, that'd be nice," said Reid, sporting a new red 49ers cap and matching tie with his tan suit.Reid and Carradine are eager to get started and meet their defensive mates, like hard-hitting safety Donte Whitner."It's a great defense, and I'm humbled to be a part of it," said Lemonier, slated as an outside linebacker.Aside from the obvious - his ability to bull through offensive linemen - Carradine earned his nickname at a young age."My mom gave it to me when I was a kid," he said. "I had an Army tank that was always with me. I always had to have it with me."And, yes, he still has the beloved toy. His mother saved it for him.The 6-foot-4, 262-pound McDonald, a strong blocker, caught 119 passes for 1,504 yards and 15 touchdowns in college.While McDonald said special teams wasn't emphasized for him at Rice considering his high repetitions on offense, he is willing to take on whatever task the 49ers ask of him. McDonald says he is "extremely underdeveloped" but plans to use his raw talent."I feel confident in my abilities to be developed however San Francisco decides," McDonald said. "I can only imagine with this next step that I'm going to improve significantly."