It wasn't emphatic, and it wasn't always pretty. But it was effective.
The US women's national team edged past Nigeria 1-0 thanks to Abby Wambach's thumping corner-kick volley just before halftime at BC Place on Tuesday, clinching first place in Women's World Cup Group D and keeping the USWNT's trophy quest on course.
The Americans were clearly the more talented side on the day, yet missed many opportunities to extend their lead and had to sweat a bit down the stretch. That said, they've picked up two wins and a draw and can now look forward to several days' rest before meeting one of the tournament's surviving third-place teams in a Round-of-16 match in Edmonton on Monday.
The US appeared to go in front just eight minutes in as the outstanding Julie Johnston fired Wambach's headed pass home from close range after Nigeria failed to clear a set piece. But the assistant referee's flag had flown up for offside, a decision that replays suggested was open to question.
USWNT goalkeeper Hope Solo was called into action four minutes later as Courtney Dike, sister of MLS veteran Bright Dike, was given far too much time and space in the US box, but could not force anything more than a straightforward save from Solo.
With Wambach restored to the starting lineup -- alongside longtime partner Alex Morgan, making her first start in months -- after playing a substitute's role against Sweden on Friday, the Americans put her target-striker skills to good use with flicks and layoffs to build possession in the first half.
But the final pass often went missing, and in a flash, Nigeria gave a warning of their danger in the 25th minute as Asisat Oshoala raced after a through ball into acres of space behind the US back line.
The speedy striker had only Solo to beat, but Johnston made a stunning recovery run to get back and block Oshoala's shot wide in the nick of time.
As time ticked away in the first half, Megan Rapinoe appealed furiously for a handball in the Nigeria box as Ngozi Okobi appeared to deflect her cross with an arm, but no penalty-kick call was forthcoming.
The Super Falcons' deep defending and physical play was frustrating the US. Yet their Achilles heel let them down with just moments left before halftime, handing Wambach a straightforward finish for her first goal of this World Cup.
Corner kicks had proved a major weak point for Nigeria and their defense was all over the shop when Rapinoe curled an outswinging delivery to the far post, where Wambach arrived to sidefoot a leaping left-footed strike into the net for a 1-0 USWNT lead.
Per U.S. Soccer, Abby Wambach has scored in the group phase of every World Cup in which she has played ('03, '07, '11, '15).— Jeff Kassouf (@JeffKassouf) June 17, 2015
Eager to sew up this result early, the US came roaring out of the gates after the break and Dede had to make a big save on Morgan in the 48th minute as the Nigerians rode their luck.
Wambach and Josephine Chukwunonye clashed heads in a frightening moment near the hour mark, with Chukwunonye requiring lengthy medical treatment and receiving a yellow card to boot.
Dede came up clutch again in the 62nd minute, diving low to block a Morgan shot and deny a certain goal. But the odds of a comeback lengthened with 20 minutes to go when defender Sarah Nnodim was shown her second yellow card for a foul on Rapinoe, leaving the Nigerians shorthanded.
But the US couldn't find a second goal to ice the game, and head coach Jill Ellis brought on veterans Christie Rampone and Shannon Boxx to help defend the lead and gave Sydney Leroux a runout up top.
Rampone's first appearance of this tournament means that she has now played in six Women's World Cups, joining select company as the fifth player ever to do so, and the second USWNTer after former teammate Kristine Lilly.
Christie Rampone is the 5th player and 2nd American to play in five Women's World Cups (Formiga, Sawa, Prinz, Lilly).— Paul Carr (@PCarrESPN) June 17, 2015
Aside from a few nervy moments in their own box, the US rarely looked troubled despite their slim advantage and the final whistle brought cheers from the large, strongly pro-US crowd. Nigeria, meanwhile, exit another WWC early despite showing signs of dramatic improvement.