After one play it looked as if the San Francisco 49ers might have it easy against the Seattle Seahawks.

Not the case, as Christian McCaffrey's 72-yard scamper on the opening play, which set up a three-yard touchdown run from Jordan Mason, did not prove a harbinger of a routine first half.

The 49ers' offense struggled to build on that electric start, but another explosive play from Deebo Samuel ensured San Francisco went into the half leading 14-10, here are our observations.

Explosives fuel the Niners

The Seahawks frustrated the 49ers for much of the first half. However, such is the talent on the San Francisco offense that the Niners can produce massive momentum-changing plays at any moment.

San Francisco illustrated that point in devastating fashion with McCaffrey's incredible opening surge and did so again as Purdy's 54-yard hookup with Samuel on third and 11 on a drive that looked to be stalling injected life into Levi's Stadium. The 49ers had seen their previous three drives end in a pair of punts and an interception.

The 49ers ended the half averaging 10.4 yards per play, with that gaudy number far from illustrative of the struggles the offense endured for large periods of the first half.

Ward hurt on opening series

The 49ers' defense was dealt a substantial blow on Seattle's opening series as Charvarius Ward, who went close to intercepting Drew Lock, came off the field with a groin injury.

San Francisco's top cornerback was seen trying to work out the injury on the sideline but did not return during the first half, and his absence was immediately felt as Drew Lock converted a third down by targeting Isaiah Oliver, who came in at slot corner with Deommodore Lenoir reverting to playing outside on nickel downs in Ward's absence.

Lock then found DK Metcalf for a 31-yard touchdown on a pinpoint throw down the left sideline. Ambry Thomas had excellent coverage, but Metcalf instantly having an impact spoke volumes about the importance of Ward to the 49er defense. 

Ward locked down Metcalf in the two teams' Thanksgiving encounter as he shadowed the Seahawks' star receiver, and the 49ers' hopes of stopping him have decreased with their number one corner out of the game.

Pressure doesn't tell

One of the most notable aspects of the first-half performance for a defense that steadily improved after the opening series was the pass rush's failure to get to Seahawks backup quarterback Drew Lock.

There were several instances where the 49ers got pressure on Lock, in for the injured Geno Smith, but it never told, with San Francisco unable to get Seattle behind the chains consistently.

San Francisco's pass rush did an excellent job last week in the blowout win over the Philadelphia Eagles of playing with discipline to prevent Jalen Hurts from finding open rush lanes. If the 49ers are to pull away in the second half, they'll need their front to make a more tangible impact.

49ers confirm inactives for Week 14, vs. Seahawks

No surprises here.