The Vikings have been active through the first week of free agency but they're not done yet. Vikings general manager Rick Spielman said on Friday that there are more visits already scheduled and the team will continue to monitor the free agency market over the next few weeks. "We're trying to be as aggressive as we can, trying to hone on specific guys that we know can come in and help our ballclub," Spielman said during a teleconference. "I think by the activity that we've done so far, it's by no means the end of what we're going to do." The Vikings focused on improving their 31st ranked defense last season in the offseason by targeting young players that would fit head coach Mike Zimmer's need. Some of their biggest signings over the last week, defense end Everson Griffen, defensive tackle Linval Joseph and cornerback Captain Munnerlyn, are all in their 20s. "We had guys that we specifically kind of honed in on that we were trying to go get, but we also had some alternatives that we wanted to look at as well," Spielman said. "But we had a specific plan in place and very pleased how that plan came together." Spielman said while the team's cap space is in good shape at the moment, most of the deals moving forward will likely be shorter. The Vikings brought in defensive tackle Henry Melton for a visit, but he left without a deal. He reportedly has other visits lined up with the Seahawks and Cowboys. Spielman said the team has contacted his agent and monitor his status. Spielman also intends to monitor defensive tackle Kevin Williams' situation. He said he spoke to Williams' agent this week. "There's no decision that's been made," Spielman said. "I told him we'd leave it open. But we were trying to address some other needs that we definitely wanted to get done first." Guard Charlie Johnson is another former player that Spielman said the team will monitor. He said he would like to bring Johnson back, but he has interest from other teams as well. Spielman wants to bring 15 offensive linemen into camp and keep at least eight on the team. "I think the more depth you can accumulate on that offensive line, it really helps your ballclub," Spielman said. "That's an area that we'll probably address in the draft as well." Along with free agency, Spielman and the Vikings front office have continued evaluating players in the draft. Spielman, along with Zimmer and offensive coordinator Norv Turner, were at Alabama's Pro Day on Wednesday. Spielman said he intends to watch college tape on Friday and Saturday before heading out to more Pro Days this week. "Between Pro Days and working on free agency, it never ends," Spielman said. "But that's part of the business and that's the exciting part. This is the time of year with this free agency and with the draft that you want to improve your ballclub, and we've got a lot of good people in place working hard in their specific areas to get that accomplished."