BOSTON — Even if it sometimes seemed like you could prepare a four-course meal in between some of his deliveries, Jon Lester succeeded yesterday in extending the Red Sox’ streak of quality starts.

In stark contrast to last month, when the team’s starters routinely forced manager Terry Francona into his bullpen in the middle of games, Boston’s starters have regularly pitched through the sixth — and often deeper — of late.

Since April 25, every Red Sox starter has pitched at least six innings. Only once — Josh Beckett on Saturday night — did the starter give up more than three earned runs, and even then, the runs against Beckett were inconsequential. By the time Beckett allowed Tampa’s fourth run Saturday night, his teammates had provided him with nine.

Dating back to April 21 — a period that included two emergency starts from minor leaguers David Pauley and Justin Masterson — the starters have compiled a collective 2.69 ERA, far below the league average ERA (4.16) going into yesterday.

Cut the sample size down to the last eight games, and the numbers become even more eye-popping. In that span, Boston starters have fashioned a 1.92 ERA.

For all the attention paid to the team’s resurgent offense — seven runs or more in each of the last three games following a five-game slump that saw them score just five runs — it’s been the starting pitching that has steered the Sox to their lead atop the American League East.

“It allows your offense some time where you’re not battling back from a deficit,” said manager Terry Francona after yesterday’s perfunctory 7-3 sweep-completing victory over Tampa Bay. “It gives your offense some times and you don’t have to go too far with your bullpen, or ask somebody to do something they’re not comfortable doing.”

“We definitely weren’t getting this earlier (in the season),” said catcher Jason Varitek on getting the starters deep into games. “It’s the key to winning. Lately, we haven’t had to ask too much of our bullpen. It may not always be that way, but it definitely came at the right time to give our bullpen a rest.”

The turning point, Varitek estimates, came when Beckett pitched eight innings against the Yankees in New York on April 21, halting a string of games in which Boston starters were being forced from the game too soon and the bullpen was suffering from overwork.

“Josh sets the tone for us,” said Varitek. “He kind of got us going.”

Since then, nearly everyone else has fallen in line, giving the Sox a consistency they can count on. Even when the team sputtered at the plate, the Sox were able to win two of those five games in which they averaged a run per contest because the starters shut down the opposition, enabling the Sox to win 1-0 and 2-1 on consecutive nights.

If the starters have straightened out, the same cannot be said of the bullpen. Closer Jonathan Papelbon is 9-for-9 in save opportunities and hasn’t walked a batter since the Red Sox left Japan. Hideki Okajima, though he’s faltered some with inherited runners (allowing all but two of eight to score this season) nonetheless has been sharp, racking up an ERA of 0.71.

But beyond Papelbon and Okajima, dependability is an issue.

Manny Delcarmen took over for Lester in the seventh, entrusted with a 4-1 lead. But after retiring the first batter he faced, Delcarmen yielded a single to Jason Bartlett and a triple to Akinori Iwamura.

When Okajima took over and allowed a single to Carl Crawford, scoring Iwamura, the Sox lead was down to a single run. That, in turn, forced Francona into going to Papelbon for a four-out save.

Delcarmen has now been scored upon in 9 of his 16 appearances this season, including 5 of his last 6. Delcarmen appeared to have turned a corner in the second half of last season, but the first 33 games this year have seen him regress.

He lacks confidence in himself, and accordingly, the Sox lack confidence in him. As for Mike Timlin, one stat tells the story: opposing batters are hitting nearly .500 (14-for-30) against him this season.

All of which makes the re-call of Craig Hansen yesterday all the more significant. Watch for Hansen to get more important innings on this road trip, as a test to see if he handle the critical setup role.

If he passes, Hansen could emerge as the team’s primary set-up man. If he doesn’t, the Sox may be forced into looking outside the organization for bullpen help to augment their late-inning duo. Given the expected cost, that’s a price the Red Sox don’t want to be forced into paying.

A year ago, following an infamous night in Buffalo, Delcarmen and Hansen took divergent paths. Delcarmen righted himself at Pawtucket and earned a position of responsibility in the Boston bullpen.

Starting tonight, it may be Hansen’s turn. And, it may come at Delcarmen’s expense.

smcadam@projo.com