The Falcons came up 10 yards short in the postseason. But in the offseason, general manager Thomas Dimitroff is clicking on all cylinders. The Falcons had some potentially massive holes at several key positions, but they have come up with plausible answers and possible upgrades at nearly every spot. The key move was to get tight end Tony Gonzalez, a future Hall of Famer, to put off his retirement for at least another season. With Gonzalez back on board, the team was more attractive to key veteran free agents. The Falcons released key contributors in running back Michael Turner, defensive end John Abraham and cornerback Dunta Robinson to clear room under the salary cap. They left enough room to keep some of their players and sign two free agents — former Pro Bowlers Steven Jackson and Osi Umenyiora, who signed with the team Thursday. The only noticeable hole remaining is at cornerback. In addition to releasing Robinson, Brent Grimes, who made $10 million last season, remains a free agent. The Falcons’ moves in free agency played a role in landing Umenyiora. “They signed some very good players,” Umenyiora said. “They are going to be able to contend for a long time here.” Umenyiora, who went to two Pro Bowls and earned two Super Bowl rings with the New York Giants, could have visited other teams.