DAVIE, Fla. -- The Miami Dolphins' offensive line, which seemed set last week, has sprung a leak. Both starting guard positions are open for battle after Saturday's 20-14 victory at Tampa Bay.

That's a bit unsettling considering the offensive line, which allowed a NFL-worst 58 sacks and blocked for a running game that was 26th in the NFL, was the No. 1 offseason priority.

On the bright side, quarterback Ryan Tannehill is getting more comfortable in the new offense and it shows. He was an efficient 9-for-14 for 110 yards, no touchdowns and no interceptions against Tampa Bay. In two preseason games he's now 15-for-20 passing for 172 yards, one touchdown and no interceptions.

"I don't what it is in particular," Tannehill said, "but I feel comfortable, I really like the system. The combinations of routes we use downfield, the combination of a quick passing game as well as downfield routes. (Offensive coordinator Bill Lazor) has made it clear if the downfield route is not there we're more than happy to check it down and take our six yards."

At right guard, second-year player Dallas Thomas was flagged twice and allowed a sack on quarterback Ryan Tannehill (by Pro Bowl defensive tackle Gerald McCoy) that resulted in a lost fumble. Thomas was replaced by rookie Billy Turner, but coach Joe Philbin said that wasn't because of Thomas' performance.

"That was the plan," Philbin said. "We were going to roll guys through there. It wasn't anything related to how he was playing. We have a lot of respect for (McCoy), he's an excellent football player. We'll take a look at the tape. There were a couple of plays he had to block better on, for sure."

At left guard, veteran Daryn Colledge, thought to be an easy choice as the starter, has begun sharing time with veteran Shelley Smith, who seemed to fall out of favor after losing starting jobs at right guard and center. But apparently Smith is back in contention, and he could even compete for the right guard job.

"We'll consider him anywhere," Philbin said. "We haven't ruled anybody out, we haven't named a starting offensive line yet. Everything's wide open still."

The running game remains a point of contention, too. Lamar Miller had three carries for three yards, and now has seven carries for 15 yards in two games. As a team the Dolphins rushed 26 times for 46 yards against the Buccaneers.

"I think we all agree we had way too many negative yardage plays in the running game," Philbin said, "so that really wasn't fixed the way I hoped it would have been."

The problem?

"Penetration," Philbin said. "A lot of penetration. We had guys in the backfield. We didn't establish an edge, they established and edge on us, got upfield on us a couple of times, penetrated and got in our backfield way too much, way too much."

Defensively the Dolphins had five sacks and caused a crucial fumble when cornerback Brent Grimes stripped wide receiver Mike Evans on the 1-yard line after a 41-yard reception. The loose ball rolled out of the corner of the end zone for a touchback. But Evans ran free because safety Jimmy Wilson hit him and didn't wrap up. The 6-foot-5 Evans bounced off the hit and kept running, evidence of the tackling issue that has plagued the Dolphins throughout training camp.

"I didn't think our tackling was very good in the first half, especially in the secondary," Philbin said. "We had some opportunities there to tackle guys and get them on the ground and we didn't. I thought we'd tackle better."

Overall, things are fairly upbeat for the Dolphins, and that's because the new offense seems to be doing well. But the problems with the offensive line and tackling have to be corrected soon or two of the major issues that plagued this team last season will plague them again this season.

Notes: Quarterback Matt Moore, who might be in a battle for the backup job with newly-signed Brady Quinn, was strong against Tampa Bay, going 13-for-19 passing for 158 yards and one touchdown. ... Running back Knowshon Moreno, activated last week from the PUP (Physically Unable to Perform) list after offseason knee surgery, should get a big share of the load in practice this week and might play against Dallas on Saturday.