When the Titans re-signed Antonio Johnson earlier this month, they added another big piece to a fortified defensive front. Johnson brings size — 330-plus pounds — and nastiness, two things defensive coordinator Jerry Gray craved heading into the offseason. “Those big guys have a role in this league. You have to be able to be physical up front,” Gray said. “You have to have a presence to stop the run, and we went out and got some really big guys.” Johnson returns to a team and a city he’s familiar with — the defensive tackle was a fifth-round pick of the Titans in 2007. He’s also set to return to the same house he bought just before his second NFL season, which was supposed to be with the Titans. Shortly after the purchase, however, the Titans released him. Then the Colts signed him. Five years later, he’s back in Nashville. Now the people renting his house have to move. “Not to be cold, but I told them we have to get back in there,” Johnson said with a smile. “It will be the house I’m paying the mortgageon, so it makes sense. … Things worked out well. I can’t complain at all.” The Titans need things to turn out well on defense. Last season the unit was pushed around frequently on the way to giving up a franchise record 471 points. After signing free agent defensive tackle Sammie Hill (6-4, 329) in March, the Titans added mammoth defensive end Ropati Pitoitua (6-8, 315) and drafted LSU defensive end Lavar Edwards (6-4, 277). It’s in the middle at tackle where the Titans should be noticeably sturdier, however. In addition to Hill and Johnson, there are Jurrell Casey (6-1, 300), Mike Martin (6-1, 305), DaJohn Harris (6-3, 306) and Zach Clayton (6-2, 299). Coaches also like what they’ve seen from undrafted free agent Stefan Charles (6-5, 302). The Titans hope the result is an improved run defense. Last year they allowed 127.2 rushing yards per game, which ranked 24th in the NFL. In eight games, they gave up more than 140 yards. Opposing runners averaged 4.2 yards per carry.