Rather than make for a long day, that early deficit instead created a frustrating one when the Mets made several stalled attempts at a comeback.
"I thought it would have given us a good lift to kind of fight our way back into this contest," manager Jerry Manuel said.
So they did their best. Helping Santana avoid further damage was Francoeur, who nailed Adam Dunn as he attempted to score on Ian Desmond's deep fly ball in the first. It seemed to be just the spark the Mets needed.
And Francoeur's throw, which appeared to be headed up the line before tailing perfectly toward home plate, was not the first to beat Dunn to the plate.
Two innings earlier, Dunn bowled over Mets catcher Rod Barajas on Willingham's grand slam, which bounced back onto the field and was initially ruled a triple. The ball squirted away, Dunn was safe at home and Willingham also tried to score, spiking Barajas in the process.
"It looked pretty scary," Willingham said of Dunn's collision. "I wouldn't want to have a 300-pound man running into me."
And none of it mattered after umpires consulted video review, ruling Willingham's hit a grand slam.
Francoeur's assist in the third proved more productive -- and not only because it gave him 71 for his career, thus widening the gap between him and everyone else in baseball. Since Francoeur broke into the big leagues in 2005, his 71 outfield assists rank well ahead of Alfonso Soriano's 58 for most in the Majors.
Assist No. 71, however, was most distinctive in that it gave the Mets a jolt. Though they weren't scoring -- listless all afternoon against old friend Livan Hernandez -- they had reason to believe they could chip away at the five-run margin.
Hernandez, however, proved to be most stubborn. Despite sharing a clubhouse with the man for most of last season, the Mets could not decipher anything their former teammate was doing on the mound. When they took pitches early in counts, Hernandez pumped strikes through the zone. When they swung away, Hernandez dumped a wide variety of breaking balls in the dirt.
"We appeared unprepared," was how Manuel put it, criticizing his hitters' inability to trust their scouting reports on Hernandez.
Though perhaps it was not that simple.
"There's a reason he's pitched so long in the big leagues," third baseman David Wright said. "He really studies hitters. He knows where hitters' weaknesses are, and he tries to exploit that."
Consider it a job well done. The Mets did not show any sort of offensive spark until Hernandez left the game of his own volition, opening the door for Jacobs to homer off reliever Brian Bruney in the eighth. With that, a lazy Sunday crowd sprung to life, tickled by the possibility of a comeback.
To fan the flames, Rodriguez helped spark a benches-clearing incident, plunking Nationals outfielder Willie Harris with a pitch in the ninth, then swapping verbal barbs with him as Saturday's hero made his way down to first. The Citi Field crowd whipped up as much of a frenzy as it could. But the climax had already come.
Against Nationals closer Matt Capps, the Mets mustered two fly balls and a strikeout. That was all, especially frustrating the Mets considering their thoughts heading into the game.
"We felt comfortable," said Francoeur. "We felt like we could score some runs, and we weren't able to today."
"We felt real confident today," shortstop Jose Reyes said, "because we had Santana."
And that may be the most significant issue of all: The Mets would like to win each and every one of Santana's starts. On Sunday, they did not.
They also did not win at home, sputtering to a 2-4 start in their first six games of the season. Now, greater challenges lie ahead on a six-game road trip to Colorado and St. Louis, followed by a daunting 10-game homestand against the Cubs, Braves and Dodgers.
"It's six games," Francoeur said, summing up the homestand. "With that being said, we'd better get it going quick, because we've got some teams coming up that are really, really good."