A 1-0 defeat to Stoke City on Boxing Day was a third in four Premier League games for Everton, and saw them slip to 12th in the Premier League table.
Martinez was frustrated by the team's profligacy in front of goal against Stoke, and expects an improvement at St James' Park as Everton aim to end their poor run of form.
He said: "We'll need to be clinical on Sunday because we weren't [against Stoke] and it cost us."
However, the Spaniard may have to make wholesale changes for the trip to Newcastle, with a number of key players set to be on the sidelines through injury and suspension.
"Tim Howard has pulled his calf, he'll have to be assessed but I'll be very surprised if he can make the game against Newcastle," Martinez added.
"Phil Jagielka had an incident where he rolled his ankle and I'd say the ligaments have been stretched and I doubt again he'll be available [either].
"John Stones [ankle] and Kevin Mirallas both did really well to finish the game and they'll be doubts for Sunday now.
"Steven Naismith picked up a yellow card and he'll be suspended."
Newcastle are also struggling for form after their revival in October and November came to an abrupt halt in December.
Having won five league games in a row from mid-October, Alan Pardew's side have only won once since - against leaders Chelsea - and come into this game on the back of three successive defeats.
The last of those came at Old Trafford on Sunday, when an injury-ravaged Newcastle were beaten 3-1 by Manchester United.
Pardew hopes to get through Sunday's game with no further problems before setting his sights on bringing in new additions.
"We had nine players not involved [against Manchester United], and that's not good enough," the Newcastle boss said. "I have my medical team under full jurisdiction to get some bodies back and maybe in January we need to get one or two in to make sure we push on in the second half of the season.
"We have had a difficult year. I think this year with new players we should have been better than perhaps we were at the start of the season, but we have done well, particularly with the young players.
"But I don't think wins [in the final games of the year] will cloud over that it has been a difficult year for Newcastle."
Jak Alnwick is expected to continue in goal against Everton with Tim Krul (ankle) and Rob Elliot (thigh) still out, while Paul Dummett is the latest injury concern having been substituted against Manchester United with a knock.
Everton are unbeaten in their last five meetings with Newcastle and have won at St James' Park in the past two seasons.
