Boston catcher Reese McGuire, left, congratulates closer Kenley Jansen after he earned a save against the Los Angeles Angels at Fenway Park on April 15. Mary Schwalm/Associated Press

ATLANTA  — Who could’ve seen this coming? Who could’ve predicted that the Boston Red Sox – a team hammered by media and critics all winter – would begin the week with the fifth-best record in the American League.

Closer Kenley Jansen could. It’s why he signed with Boston as a free agent.

“Look around,” Jansen told me Sunday in Philadelphia. “(Justin) Turner’s a winner. (Adam) Duvall. Macho Man (Masataka Yoshida). They brought winners in here. I knew we’d be good.”

Being on a good team matters to Jansen, because good teams give closers more save opportunities. Jansen’s next save will be his 400th, a level only achieved by six other pitchers in history. If he continues to rack up saves for another couple of years he will greatly enhance his Hall of Fame credentials.

Jansen picked up the 399th save of his career Saturday night when he closed out a 7-4 win at Philadelphia. It was Boston’s eighth straight win, its longest winning streak since 2021. That run ended Sunday when the Phillies took the final game of the series.

The unexpected surge was powered by a relentless offense. The Red Sox have scored the third-most runs in all of baseball. They have the most hits. They’re second in batting average, fourth in OPS and fifth in home runs.

Rafael Devers leads the American League in homers with 11. Yoshida has a 16-game hitting streak and is batting .321. Jarren Duran is hitting .366 since being called up April 17.

The offense has been there from the start. Quietly, Boston’s much-maligned starters have rounded into form to support the bats.

Over the last nine games the Red Sox rotation has walked fewer than 1.5 batters per start. Starters’ ERA in that span is nearly two runs a game lower than the full-season average.

Chris Sale has a 3.86 ERA in his last four starts with 10-to-1 strikeout-to-walk ratio. He hit 99 mph Friday night, the hardest he has thrown in four years. He might once again be the ace the team has desperately been looking for.

In fact, Boston pitchers have gone five or more innings in 12 straight starts, the team’s longest run in two years.

“It’s something that we envisioned with this rotation,” said Manager Alex Cora. “You know, five or six innings and then move on. We’re at a stage of taking care of them, you know, they can go 100 pitches, seven innings, all that stuff.”

The biggest challenge is the division. The AL East might just be the toughest division in the history of baseball. The Rays are off to a historically good start – the Sox have won 8 of 10, and didn’t pick up a game in the standings. Only four AL teams have better records than Boston, and three are in the East.

If the Sox can tread water against the division – they’re .500 against AL East teams right now – and take care of business against the rest of the competition they will be able to stay in the playoff race. And that’s a lot better than most people expected.

In spring training we said there was a 2013 vibe in the clubhouse at Fort Myers, Florida. Veterans came in and have become leaders. Young players are responding to the new voices in the room. Cora loves the makeup of his team.

So does Jansen. He’s fully confident he will get a chance to pick up his 400th save in the coming days. That’s why he came to Boston.

Tom Caron is a studio host for the Red Sox broadcast on NESN. His column appears in the Portland Press Herald on Tuesdays.