SAN FRANCISCO -- On the surface, Giants reliever Steve Kline is affable-plus, often roaming the clubhouse ready for hijinks and jokes to keep teammates loose.

He doesn't throw out one-liners on the mound -- he's serious all the time -- and the 35-year-old left-hander was not amused over his shortcomings in 2006, when he felt he let the club down at critical times, especially in games at AT&T Park.

"I didn't do enough to keep the bullpen tight, didn't do a better job to get it together," said Kline on Friday.

The Giants disagreed with that self-assessment by re-signing the free agent to a two-year deal worth $3.5 million.

One of the game's best southpaw relievers, Kline leads all Major League pitchers with 682 appearances since 1998, and although he struggled in stretches, he finished the year with a flourish, going 2-0 with a save and a 2.45 ERA over his final 22 outings.

"Bringing Steve back into the fold solidifies a major part of our bullpen puzzle," said Giants general manager Brian Sabean. "It is certainly a huge advantage to have someone in the late innings that can take the ball everyday and consistently get tough left-handed hitters out."

Overall, Kline was 4-3 with a 3.66 ERA, considerably better than his previous season with Baltimore, when he gave up 11 homers over 61 innings and had a 4.28 ERA. Better conditioning and a loss of about 40 pounds helped Kline rebound.

Kline had great numbers on the road -- 2.08 ERA and a .213 average against -- yet had little success at home, going 1-2 with a 5.26 ERA and .327 average against in 38 home games.

"I always put too much pressure on myself at home," said Kline. "When you're booed on the road, you know you're doing well, but getting booed at home is bad. When you pitch in your hometown, you don't want to make a fool of yourself."

Despite his finger-wagging -- at himself -- Kline expects a good season from himself and the club in 2007. The young bullpenners are older and more experienced now, and it won't be another transition year for him.

"We know what we have to do to be a lot better than last year as a whole," said Kline. "We'll be more calm and know what to expect now, just going out there and pitching."

With Kline's return, it could make room for prized left-handed rookie Jonathan Sanchez to move toward the rotation. He starred in the bullpen last year, but is being groomed as a much-needed starter next season.

Kline, a 10-year big leaguer, said he was delighted with the two-year pact and was pleased with sitting on the sidelines watching Sabean deal with new signings.

"I have a good feeling with Sabean," Kline said. "He's honest in what he tells you, and it's always better when you know you're going to be on a team for a while."

Kline said it was a difficult transition working with rookie catcher Eliezer Alfonzo after his longtime St. Louis backstop Mike Matheny suffered a serious concussion in late May that ended his season.

But he watched Alfonzo improve despite having to, as Kline said, "consume so much information. If [new catcher] Bengie Molina is anything like his little brother, [Cardinals backstop] Yadier, it'll be great."

Sabean said Friday he has talked to Matheny following the latter's midweek medical examination, but that the veteran didn't disclose results of the tests.

"When he has an idea of how he wants to get [concussion symptoms] resolved, he and the Giants will get together," said Sabean.