The finish line loomed as clearly as the serve line when Sam Querrey slammed a love hold for a 4-2 fourth-set lead. Digging into the red dirt with defiance, James Ward refused to let a twitchy Querrey get any closer.

Playing catch-up much of the match, the 175th-ranked Ward broke serve five times in a row, reeling off  10 of the last 11 games to stun Querrey, 1-6, 7-6 (3), 3-6, 6-4, 6-1 and stake Great Britain to a 2-0 lead over the United States in the Davis Cup World Group tie at Petco Park.

Make no mistake, Ward played bolder tennis at crunch time and competed with more energy, belief and grit in twice fighting off triple break point. But Querrey completely collapsed down the stretch suffering an absolutely brutal loss that will surely haunt the world No. 49, who spent the final set wandering around the court wearing the vacant look of a man with no answers for the hard-charging Ward.

It was a match of wild momentum shifts as Querrey stormed to a 5-0 lead after a mere 17 minutes of play on the strength of an imposing three-ace game. Querrey's inability to convert break points — he converted just 5 of 18 break point chances — proved costly when Ward dug out of a love-40 hole to hold for a 4-3 second-set lead.

Tension tightened the arms of both men in the tiebreaker — then Querrey cracked. The American bricked a routine forehand volley to fall behind 1-3. Two points later, Ward sent a flat forehand into net and it was 3-all. Charging forward, Querrey netted a low forehand volley to donate the mini-break. Ward showed guts, ripping a forehand winner that singed the sideline for 5-3 and an increasingly tight Querrey clanked successive errors as an Ward snatched the tie breaker to level the match without a single break point.

The 26-year-old Ward blinked in his first service game, whacking a double fault off the tape to face double break point before missing a backhand wide to gift the break and a 2-0 third-set lead. Shadows crept over the court as Querrey quickly consolidated for 3-0 then raced to triple break point lead in the ensuing game. Ward withstood the challenge digging out a 0-40 hold for the second time in the match for 1-3. Those wasted opportunities highlight an issue that holds Querrey back: He sometimes seems mentally adrift and doesn't always play pivotal points with the required urgency or care. Still, Querrey closed the third set at love on the strength of three forehand winners.

When the California native opened a 4-2 lead in the fourth he seemed to be in cruise control just eight points from the finish. But Ward, the tough-minded son of a London cab driver, showed a fierce appetite for the fight as court conditions slowed, an increasingly weary Querrey began losing some sting off his first serve and Ward began reading the second serve. Ward's backhand is a better weapon than his forehand, but Querrey inexplicably played the Brit's backhand side. Ward is quicker around the court and began to draw Querrey out of his comfort zone on the baseline, buzzing a backhand pass crosscourt for break point and earning his first break when Querrey sailed a forehand to level the set at 4-all. It took Ward more than two-and-a-half hours to finally break serve, but when he did, Querrey's spirit snapped.

When Ward tormented Querrey, drawing him forward with another drop shot then flicking a lob winner to hold for a 3-0 fifth set lead, the entire British bench sprung to its feet making nearly more noise than what remained of a depleted American crowd. Querrey, who dropped to 2-8 in five-setters, is an affable man, but failed to bring the emotional fire to engage the crowd, exhibited an alarming inability to adjust and spent the final set in a downward spiral while Ward punctuated winners with roaring affirmations. Ward won 13 of 19 points played on Querrey's serve in the decider, slamming a smash to seal a rousing comeback and put Great Britain one win away from its first Davis Cup win over the USA in 79 years.