He says Ōtūmoetai have added 10 new young players to the squad this year, and have had wins in pre-season games against Ngaruawahia Panthers and Pāpāmoa.
Sundborn says he believes his side has it in them to beat the defending champs this weekend.
"We are as fit as we can be at the start of the season. It is a big test against the Waikato champs and we will have to be patient and trust ourselves and what we have been training to do," Sundborn says.
"As long as they don't get overawed, we will be alright and if we are going to beat them it will be on our home ground.
"We are more of a mobile squad but my main focus was to get them fit and then they will a enjoy their league a bit more."
The two Tauranga sides have joined the Waikato league after competing in combinations of Coastline and Bay of Plenty competitions in recent years. Sundborn says they chose to play in the Waikato competition in search of tougher competition.
And a tough competition is what Pāpāmoa coach Jock Nicholson is expecting.
"We are in a bit of a development phase, but if you don't have a crack you don't know where you are at," Nicholson says.
"We have had a reserve grade team for a couple of years and since 2017 we have built a good culture. It has been challenging but we are hanging in there.
"The Bay of Plenty comp was good, and there is a little more travel with the Waikato competition. The reserve grade level is a good level as well and we are expecting tough games week in, week out."
Pāpāmoa reserves began their campaign last Saturday with a 38-22 win over the Ngaruawāhia Lions.
The reserve grade fixtures mirror those of their premier sides throughout the year and Nicholson says it is great for a club to have both sides at one venue on game day.
He says the Waikato teams are not foreign to the club, having played against them in past competitions.
"Like any coach, we want to win. For me it is about improving and development and to get two teams was a mammoth achievement. We have retained and attracted players, we are all passionate about rugby league and want to be the best we can be on the day.
"We have some size about us with some big forwards, but we have to play what is in front of us. I would like to think we play a forward orientated game, but you can't rely on that if you want to progress to the finals."
Waikato Rugby League premier competition first round:
Ōtūmoetai Eels v Taniwharau, Mitchell Park, 3pm.
Ngaruawāhia Panthers v Hamilton Hornets, League Park, 3pm.
Turangawaewae v College Old Boys, Paterson Park, 3pm.
Pāpāmoa Bulldogs v Hamilton City Tigers, Gordon Spratt Reserve, 3pm.
Hukanui bye.
